<row>
<entry><type>money</type></entry>
<entry></entry>
- <entry>US-style currency</entry>
+ <entry>currency amount</entry>
</row>
<row>
<para>
Numeric types consist of two-, four-, and eight-byte integers,
- four- and eight-byte
- floating-point numbers and fixed-precision decimals.
+ four- and eight-byte floating-point numbers, and fixed-precision
+ decimals. <xref linkend="datatype-numeric-table"> lists the
+ available types.
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-numeric-table">
<title>Numeric Types</title>
<tgroup cols="4">
<thead>
<row>
<entry><type>smallint</></entry>
<entry>2 bytes</entry>
- <entry>Fixed-precision</entry>
+ <entry>small range fixed-precision</entry>
<entry>-32768 to +32767</entry>
</row>
<row>
<entry><type>integer</></entry>
<entry>4 bytes</entry>
- <entry>Usual choice for fixed-precision</entry>
+ <entry>usual choice for fixed-precision</entry>
<entry>-2147483648 to +2147483647</entry>
</row>
<row>
<entry><type>bigint</></entry>
<entry>8 bytes</entry>
- <entry>Very large range fixed-precision</entry>
+ <entry>large range fixed-precision</entry>
<entry>-9223372036854775808 to 9223372036854775807</entry>
</row>
<row>
<entry><type>bigserial</type></entry>
<entry>8 bytes</entry>
- <entry>autoincrementing integer</entry>
+ <entry>large autoincrementing integer</entry>
<entry>1 to 9223372036854775807</entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
<para>
The syntax of constants for the numeric types is described in
<type>int</type>) and <type>smallint</type>. The type
<type>bigint</type>, and the type names <type>int2</type>,
<type>int4</type>, and <type>int8</type> are extensions, which
- are shared with various other RDBMS products.
+ are shared with various other SQL database systems.
</para>
<note>
values to any particular scale, whereas <type>numeric</type> columns
with a declared scale will coerce input values to that scale.
(The SQL standard requires a default scale of 0, i.e., coercion to
- integer accuracy. We find this a bit useless. If you're concerned about
+ integer precision. We find this a bit useless. If you're concerned about
portability, always specify the precision and scale explicitly.)
</para>
<para>
The data types <type>real</type> and <type>double
precision</type> are inexact, variable-precision numeric types.
- In practice, these types are usually implementations of <acronym>IEEE</acronym> 754
- binary floating point (single and double precision,
- respectively), to the extent that the underlying processor,
- operating system, and compiler support it.
+ In practice, these types are usually implementations of
+ <acronym>IEEE</acronym> Standard 754 for Binary Floating-Point
+ Arithmetic (single and double precision, respectively), to the
+ extent that the underlying processor, operating system, and
+ compiler support it.
</para>
<para>
Thus, we have created an integer column and arranged for its default
values to be assigned from a sequence generator. A <literal>NOT NULL</>
- constraint is applied to ensure that a NULL value cannot be explicitly
+ constraint is applied to ensure that a null value cannot be explicitly
inserted, either. In most cases you would also want to attach a
<literal>UNIQUE</> or <literal>PRIMARY KEY</> constraint to prevent
duplicate values from being inserted by accident, but this is
<title>Monetary Type</title>
<note>
- <title>Deprecated</title>
+ <title>Note</title>
<para>
The <type>money</type> type is deprecated. Use
<type>numeric</type> or <type>decimal</type> instead, in
<para>
The <type>money</type> type stores a currency amount with fixed
- decimal point representation. The output format is
+ decimal point representation; see <xref
+ linkend="datatype-money-table">. The output format is
locale-specific.
</para>
Output is in the latter form.
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-money-table">
<title>Monetary Types</title>
<tgroup cols="4">
<thead>
<row>
<entry>money</entry>
<entry>4 bytes</entry>
- <entry>Fixed-precision</entry>
+ <entry>currency amount</entry>
<entry>-21474836.48 to +21474836.47</entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
</sect1>
<see>character strings</see>
</indexterm>
- <table tocentry="1">
+ <table id="datatype-character-table">
<title>Character Types</title>
<tgroup cols="2">
<thead>
<tbody>
<row>
<entry><type>character(<replaceable>n</>)</type>, <type>char(<replaceable>n</>)</type></entry>
- <entry>Fixed-length blank padded</entry>
+ <entry>fixed-length, blank padded</entry>
</row>
<row>
<entry><type>character varying(<replaceable>n</>)</type>, <type>varchar(<replaceable>n</>)</type></entry>
- <entry>Variable-length with limit</entry>
+ <entry>variable-length with limit</entry>
</row>
<row>
<entry><type>text</type></entry>
- <entry>Variable unlimited length</entry>
+ <entry>variable unlimited length</entry>
</row>
</tbody>
</tgroup>
</table>
+ <para>
+ <xref linkend="datatype-character-table"> shows the
+ general-purpose character types available in PostgreSQL.
+ </para>
+
<para>
<acronym>SQL</acronym> defines two primary character types:
<type>character(<replaceable>n</>)</type> and <type>character
<para>
There are two other fixed-length character types in
- <productname>PostgreSQL</productname>. The <type>name</type> type
+ <productname>PostgreSQL</productname>, shown in <xref linkend="datatype-character-special-table">.
+ The <type>name</type> type
exists <emphasis>only</emphasis> for storage of internal catalog
names and is not intended for use by the general user. Its length
is currently defined as 64 bytes (63 usable characters plus terminator)
enumeration type.
</para>
- <table tocentry="1">
+ <table id="datatype-character-special-table">
<title>Specialty Character Types</title>
<tgroup cols="3">
<thead>
</thead>
<tbody>
<row>
- <entry>"char"</entry>
+ <entry><type>"char"</type></entry>
<entry>1 byte</entry>
- <entry>Single character internal type</entry>
+ <entry>single character internal type</entry>
</row>
<row>
- <entry>name</entry>
+ <entry><type>name</type></entry>
<entry>64 bytes</entry>
- <entry>Sixty-three character internal type</entry>
+ <entry>sixty-three character internal type</entry>
</row>
</tbody>
</tgroup>
<sect1 id="datatype-binary">
<title>Binary Strings</title>
<para>
- The <type>bytea</type> data type allows storage of binary strings.
+ The <type>bytea</type> data type allows storage of binary strings;
+ see <xref linkend="datatype-binary-table">.
</para>
- <table tocentry="1">
+ <table id="datatype-binary-table">
<title>Binary String Types</title>
<tgroup cols="3">
<thead>
</table>
<para>
- A binary string is a sequence of octets that does not have either a
- character set or collation associated with it. <type>Bytea</type>
- specifically allows storing octets of zero value and other
- <quote>non-printable</quote> octets.
+ A binary string is a sequence of octets (or bytes). Binary
+ strings are distinguished from characters strings by two
+ characteristics: First, binary strings specifically allow storing
+ octets of zero value and other <quote>non-printable</quote>
+ octets. Second, operations on binary strings process the actual
+ bytes, whereas the encoding and processing of character strings
+ depends on locale settings.
</para>
<para>
- Octets of certain values <emphasis>must</emphasis> be escaped (but all
- octet values <emphasis>may</emphasis> be escaped) when used as part of
- a string literal in an <acronym>SQL</acronym> statement. In general,
- to escape an octet, it is converted into the three-digit octal number
+ When entering <type>bytea</type> values, octets of certain values
+ <emphasis>must</emphasis> be escaped (but all octet values
+ <emphasis>may</emphasis> be escaped) when used as part of a string
+ literal in an <acronym>SQL</acronym> statement. In general, to
+ escape an octet, it is converted into the three-digit octal number
equivalent of its decimal octet value, and preceded by two
backslashes. Some octet values have alternate escape sequences, as
shown in <xref linkend="datatype-binary-sqlesc">.
</para>
<table id="datatype-binary-sqlesc">
- <title><acronym>SQL</acronym> Literal Escaped Octets</title>
+ <title><type>bytea</> Literal Escaped Octets</title>
<tgroup cols="5">
<thead>
<row>
<tbody>
<row>
- <entry> <literal> 0 </literal> </entry>
- <entry> zero octet </entry>
- <entry> <literal> '\\000' </literal> </entry>
- <entry> <literal> select '\\000'::bytea; </literal> </entry>
- <entry> <literal> \000 </literal></entry>
+ <entry>0</entry>
+ <entry>zero octet</entry>
+ <entry><literal>'\\000'</literal></entry>
+ <entry><literal>SELECT '\\000'::bytea;</literal></entry>
+ <entry><literal>\000</literal></entry>
</row>
<row>
- <entry> <literal> 39 </literal> </entry>
- <entry> single quote </entry>
- <entry> <literal> '\'' or '\\047' </literal> </entry>
- <entry> <literal> select '\''::bytea; </literal></entry>
- <entry> <literal> ' </literal></entry>
+ <entry>39</entry>
+ <entry>single quote</entry>
+ <entry><literal>'\''</literal> or <literal>'\\047'</literal></entry>
+ <entry><literal>SELECT '\''::bytea;</literal></entry>
+ <entry><literal>'</literal></entry>
</row>
<row>
- <entry> <literal>92</literal> </entry>
- <entry> backslash </entry>
- <entry> <literal> '\\\\' or '\\134' </literal> </entry>
- <entry> <literal> select '\\\\'::bytea; </literal></entry>
- <entry> <literal> \\ </literal></entry>
+ <entry>92</entry>
+ <entry>backslash</entry>
+ <entry><literal>'\\\\'</literal> or <literal>'\\134'</literal></entry>
+ <entry><literal>SELECT '\\\\'::bytea;</literal></entry>
+ <entry><literal>\\</literal></entry>
</row>
</tbody>
</table>
<para>
- Note that the result in each of the examples above was exactly one
+ Note that the result in each of the examples in <xref linkend="datatype-binary-sqlesc"> was exactly one
octet in length, even though the output representation of the zero
octet and backslash are more than one character. <type>Bytea</type>
output octets are also escaped. In general, each
</para>
<table id="datatype-binary-resesc">
- <title><acronym>SQL</acronym> Output Escaped Octets</title>
+ <title><type>bytea</> Output Escaped Octets</title>
<tgroup cols="5">
<thead>
<row>
<tbody>
<row>
- <entry> <literal> 92 </literal> </entry>
- <entry> backslash </entry>
- <entry> <literal> \\ </literal> </entry>
- <entry> <literal> select '\\134'::bytea; </literal></entry>
- <entry> <literal> \\ </literal></entry>
+ <entry>92</entry>
+ <entry>backslash</entry>
+ <entry><literal>\\</literal></entry>
+ <entry><literal>SELECT '\\134'::bytea;</literal></entry>
+ <entry><literal>\\</literal></entry>
</row>
<row>
- <entry> <literal> 0 to 31 and 127 to 255 </literal> </entry>
- <entry> <quote>non-printable</quote> octets </entry>
- <entry> <literal> \### (octal value) </literal> </entry>
- <entry> <literal> select '\\001'::bytea; </literal> </entry>
- <entry> <literal> \001 </literal></entry>
+ <entry>0 to 31 and 127 to 255</entry>
+ <entry><quote>non-printable</quote> octets</entry>
+ <entry><literal>\### (octal value)</literal></entry>
+ <entry><literal>SELECT '\\001'::bytea;</literal></entry>
+ <entry><literal>\001</literal></entry>
</row>
<row>
- <entry> <literal> 32 to 126 </literal> </entry>
- <entry> <quote>printable</quote> octets </entry>
- <entry> ASCII representation </entry>
- <entry> <literal> select '\\176'::bytea; </literal> </entry>
- <entry> <literal> ~ </literal></entry>
+ <entry>32 to 126</entry>
+ <entry><quote>printable</quote> octets</entry>
+ <entry>ASCII representation</entry>
+ <entry><literal>SELECT '\\176'::bytea;</literal></entry>
+ <entry><literal>~</literal></entry>
</row>
</tbody>
</table>
<para>
- <acronym>SQL</acronym> string literals (input strings) must be
- preceded with two backslashes due to the fact that they must pass
- through two parsers in the PostgreSQL backend. The first backslash
- is interpreted as an escape character by the string-literal parser,
- and therefore is consumed, leaving the octets that follow.
- The remaining backslash is recognized by the <type>bytea</type> input
- function as the prefix of a three digit octal value. For example, a string
- literal passed to the backend as <literal>'\\001'</literal> becomes
+ To use the <type>bytea</type> escaped octet notation, string
+ literals (input strings) must contain two backslashes due because
+ they must pass through two parsers in the PostgreSQL server. The
+ first backslash is interpreted as an escape character by the
+ string-literal parser, and therefore is consumed, leaving the
+ characters that follow. The remaining backslash is recognized by
+ the <type>bytea</type> input function as the prefix of a three
+ digit octal value. For example, a string literal passed to the
+ backend as <literal>'\\001'</literal> becomes
<literal>'\001'</literal> after passing through the string-literal
parser. The <literal>'\001'</literal> is then sent to the
- <type>bytea</type> input function, where it is converted to a single
- octet with a decimal value of 1.
+ <type>bytea</type> input function, where it is converted to a
+ single octet with a decimal value of 1.
</para>
<para>
backslashes in the string passed to the <type>bytea</type> input function,
which interprets them as representing a single backslash.
For example, a string literal passed to the
- backend as <literal>'\\\\'</literal> becomes <literal>'\\'</literal>
+ server as <literal>'\\\\'</literal> becomes <literal>'\\'</literal>
after passing through the string-literal parser. The
<literal>'\\'</literal> is then sent to the <type>bytea</type> input
function, where it is converted to a single octet with a decimal
escape character.
</para>
- <para>
- <type>Bytea</type> provides most of the functionality of the binary
- string type per SQL99 section 4.3. A comparison of SQL99 Binary
- Strings and PostgreSQL <type>bytea</type> is presented in
- <xref linkend="datatype-binary-compat-comp">.
- </para>
-
- <table id="datatype-binary-compat-comp">
- <title>Comparison of SQL99 Binary String and PostgreSQL
- <type>BYTEA</type> types</title>
- <tgroup cols="2">
- <thead>
- <row>
- <entry>SQL99</entry>
- <entry><type>BYTEA</type></entry>
- </row>
- </thead>
-
- <tbody>
- <row>
- <entry> Name of data type <type>BINARY LARGE OBJECT</type>
- or <type>BLOB</type> </entry>
- <entry> Name of data type <type>BYTEA</type> </entry>
- </row>
-
- <row>
- <entry> Sequence of octets that does not have either a character set
- or collation associated with it. </entry>
- <entry> same </entry>
- </row>
-
- <row>
- <entry> Described by a binary data type descriptor containing the
- name of the data type and the maximum length
- in octets</entry>
- <entry> Described by a binary data type descriptor containing the
- name of the data type with no specific maximum length
- </entry>
- </row>
-
- <row>
- <entry> All binary strings are mutually comparable in accordance
- with the rules of comparison predicates.</entry>
- <entry> same</entry>
- </row>
-
- <row>
- <entry> Binary string values can only be compared for equality.
- </entry>
- <entry> Binary string values can be compared for equality, greater
- than, greater than or equal, less than, less than or equal
- </entry>
- </row>
-
- <row>
- <entry> Operators operating on and returning binary strings
- include concatenation, substring, overlay, and trim</entry>
- <entry> Operators operating on and returning binary strings
- include concatenation, substring, and trim. The
- <literal>leading</literal> and <literal>trailing</literal>
- arguments for trim are not yet implemented.
- </entry>
- </row>
-
- <row>
- <entry> Other operators involving binary strings
- include length, position, and the like predicate</entry>
- <entry> same</entry>
- </row>
-
- <row>
- <entry> A binary string literal is comprised of an even number of
- hexadecimal digits, in single quotes, preceded by <quote>X</quote>,
- e.g. <literal>X'1a43fe'</literal></entry>
- <entry> A binary string literal is comprised of octets
- escaped according to the rules shown in
- <xref linkend="datatype-binary-sqlesc"> </entry>
- </row>
- </tbody>
- </tgroup>
- </table>
- </sect1>
+ <para>
+ The SQL standard defines a different binary string type, called
+ <type>BLOB</type> or <type>BINARY LARGE OBJECT</type>. The input
+ format is different compared to <type>bytea</type>, but the
+ provided functions and operators are mostly the same.
+ </para>
+ </sect1>
<sect1 id="datatype-datetime">
<para>
<productname>PostgreSQL</productname> supports the full set of
- <acronym>SQL</acronym> date and time types.
+ <acronym>SQL</acronym> date and time types, shown in <xref
+ linkend="datatype-datetime-table">.
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-datetime-table">
<title>Date/Time Types</title>
<tgroup cols="6">
<thead>
</tbody>
</tgroup>
</table>
- </para>
<para>
- <type>time</type>, <type>timestamp</type>, and <type>interval</type>
- accept an
- optional precision value <replaceable>p</replaceable> which
- specifies the number of fractional digits retained in the seconds
- field. By default, there is no explicit bound on precision. The
- allowed range of <replaceable>p</replaceable> is from 0 to 6.
+ <type>time</type>, <type>timestamp</type>, and
+ <type>interval</type> accept an optional precision value
+ <replaceable>p</replaceable> which specifies the number of
+ fractional digits retained in the seconds field. By default, there
+ is no explicit bound on precision. The allowed range of
+ <replaceable>p</replaceable> is from 0 to 6 for the
+ <type>timestamp</type> and <type>interval</type> types, 0 to 13
+ for the <type>time</type> types.
</para>
<note>
<para>
- When timestamps are stored as double precision floating-point
+ When <type>timestamp</> values are stored as double precision floating-point
numbers (currently the default), the effective limit of precision
may be less than 6, since timestamp values are stored as seconds
since 2000-01-01. Microsecond precision is achieved for dates within
outside that range are in <acronym>UTC</acronym>.
</para>
+ <para>
+ The type <type>time with time zone</type> is defined by the SQL
+ standard, but the definition exhibits properties which lead to
+ questionable usefulness. In most cases, a combination of
+ <type>date</type>, <type>time</type>, <type>timestamp without time
+ zone</type> and <type>timestamp with time zone</type> should
+ provide a complete range of date/time functionality required by
+ any application.
+ </para>
+
<para>
The types <type>abstime</type>
and <type>reltime</type> are lower precision types which are used internally.
or <literal>SET DateStyle TO 'NonEuropean'</literal>
specifies the variant <quote>month before day</quote>, the command
<literal>SET DateStyle TO 'European'</literal> sets the variant
- <quote>day before month</quote>. The <literal>ISO</literal> style
- is the default but this default can be changed at compile time or at run time.
+ <quote>day before month</quote>.
</para>
<para>
in single quotes, like text strings. Refer to
<xref linkend="sql-syntax-constants-generic"> for more
information.
- <acronym>SQL9x</acronym> requires the following syntax
+ <acronym>SQL</acronym> requires the following syntax
<synopsis>
<replaceable>type</replaceable> [ (<replaceable>p</replaceable>) ] '<replaceable>value</replaceable>'
</synopsis>
</para>
<sect3>
- <title><type>date</type></title>
+ <title>Dates</title>
<indexterm>
<primary>date</primary>
</indexterm>
<para>
- The following are some possible inputs for the <type>date</type> type.
+ <xref linkend="datatype-datetime-date-table"> shows some possible
+ inputs for the <type>date</type> type.
+ </para>
- <table tocentry="1">
+ <table id="datatype-datetime-date-table">
<title>Date Input</title>
<tgroup cols="2">
<thead>
<tbody>
<row>
<entry>January 8, 1999</entry>
- <entry>Unambiguous</entry>
+ <entry>unambiguous</entry>
</row>
<row>
<entry>1999-01-08</entry>
</row>
<row>
<entry>1999.008</entry>
- <entry>Year and day of year</entry>
+ <entry>year and day of year</entry>
</row>
<row>
<entry>99008</entry>
- <entry>Year and day of year</entry>
+ <entry>year and day of year</entry>
</row>
<row>
<entry>J2451187</entry>
</row>
<row>
<entry>January 8, 99 BC</entry>
- <entry>Year 99 before the Common Era</entry>
+ <entry>year 99 before the Common Era</entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
</sect3>
<sect3>
- <title><type>time [ ( <replaceable>p</replaceable> ) ] [ without time zone ]</type></title>
+ <title>Times</title>
<indexterm>
<primary>time</primary>
<primary>time without time zone</primary>
<secondary>time</secondary>
</indexterm>
+ <indexterm>
+ <primary>time with time zone</primary>
+ <secondary>data type</secondary>
+ </indexterm>
<para>
- Per SQL99, this type can be specified as <type>time</type> or
+ The <type>time</type> type can be specified as <type>time</type> or
as <type>time without time zone</type>. The optional precision
<replaceable>p</replaceable> should be between 0 and 13, and
defaults to the precision of the input time literal.
</para>
<para>
- The following are valid <type>time</type> inputs.
+ <xref linkend="datatype-datetime-time-table"> shows the valid <type>time</type> inputs.
+ </para>
- <table tocentry="1">
+ <table id="datatype-datetime-time-table">
<title>Time Input</title>
<tgroup cols="2">
<thead>
</row>
<row>
<entry><literal>04:05 AM</literal></entry>
- <entry>Same as 04:05; AM does not affect value</entry>
+ <entry>same as 04:05; AM does not affect value</entry>
</row>
<row>
<entry><literal>04:05 PM</literal></entry>
- <entry>Same as 16:05; input hour must be <= 12</entry>
+ <entry>same as 16:05; input hour must be <= 12</entry>
</row>
<row>
<entry><literal>allballs</literal></entry>
- <entry>Same as 00:00:00</entry>
+ <entry>same as 00:00:00</entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
- </sect3>
-
- <sect3>
- <title><type>time [ ( <replaceable>precision</replaceable> ) ] with time zone</type></title>
-
- <indexterm>
- <primary>time with time zone</primary>
- <secondary>data type</secondary>
- </indexterm>
- <indexterm>
- <primary>time</primary>
- <secondary>data type</secondary>
- </indexterm>
-
- <para>
- This type is defined by SQL92, but the definition exhibits
- properties which lead to questionable usefulness. In
- most cases, a combination of <type>date</type>,
- <type>time</type>, <type>timestamp without time zone</type>
- and <type>timestamp with time zone</type>
- should provide a complete range of date/time functionality
- required by any application.
- </para>
<para>
- The optional precision
- <replaceable>p</replaceable> should be between 0 and 13, and
- defaults to the precision of the input time literal.
+ The type <type>time with time zone</type> accepts all input also
+ legal for the <type>time</type> type, appended with a legal time
+ zone, as shown in <xref
+ linkend="datatype-datetime-timetz-table">.
</para>
- <para>
- <type>time with time zone</type> accepts all input also legal
- for the <type>time</type> type, appended with a legal time zone,
- as follows:
-
- <table tocentry="1">
+ <table id="datatype-datetime-timetz-table">
<title>Time With Time Zone Input</title>
<tgroup cols="2">
<thead>
</tbody>
</tgroup>
</table>
- </para>
<para>
Refer to <xref linkend="datatype-timezone-table"> for
</sect3>
<sect3>
- <title><type>timestamp [ (<replaceable>precision</replaceable>) ] without time zone</type></title>
+ <title>Time stamps</title>
+
+ <indexterm>
+ <primary>timestamp</primary>
+ <secondary>data type</secondary>
+ </indexterm>
<indexterm>
<primary>timestamp without time zone</primary>
</indexterm>
<para>
- Valid input for the <type>timestamp [ (<replaceable>p</replaceable>) ] without time zone</type>
- type consists of a concatenation
- of a date and a time, followed by an optional <literal>AD</literal> or
- <literal>BC</literal>, followed by an optional time zone. (See below.)
- Thus
+ Time stamp types exist as <type>timestamp [
+ (<replaceable>p</replaceable>) ]</type>, <type>timestamp [
+ (<replaceable>p</replaceable>) ] without time zone</type> and
+ <type>timestamp [ (<replaceable>p</replaceable>) ] without time
+ zone</type>. A plain <type>timestamp</type> is equivalent to
+ <type>timestamp without timezone</type>.
+ </para>
+
+ <para>
+ Valid input for the time stamp types consists of a concatenation
+ of a date and a time, followed by an optional
+ <literal>AD</literal> or <literal>BC</literal>, followed by an
+ optional time zone. (See <xref
+ linkend="datatype-timezone-table">.) Thus
<programlisting>
1999-01-08 04:05:06
+</programlisting>
+ and
+<programlisting>
+1999-01-08 04:05:06 -8:00
</programlisting>
- is a valid <type>timestamp without time zone</type> value that
- is <acronym>ISO</acronym>-compliant.
- In addition, the wide-spread format
+ are valid values, which follow the <acronym>ISO</acronym> 8601
+ standard. In addition, the wide-spread format
<programlisting>
January 8 04:05:06 1999 PST
<para>
The optional precision
- <replaceable>p</replaceable> should be between 0 and 13, and
+ <replaceable>p</replaceable> should be between 0 and 6, and
defaults to the precision of the input <type>timestamp</type> literal.
</para>
resulting date/time value is derived from the explicit date/time
fields in the input value, and is not adjusted for time zone.
</para>
- </sect3>
-
- <sect3>
- <title><type>timestamp [ (<replaceable>precision</replaceable>) ] with time zone</type></title>
-
- <indexterm>
- <primary>timestamp</primary>
- <secondary>data type</secondary>
- </indexterm>
-
- <para>
- Valid input for the <type>timestamp</type> type consists of a concatenation
- of a date and a time, followed by an optional <literal>AD</literal> or
- <literal>BC</literal>, followed by an optional time zone. (See below.)
- Thus
-
-<programlisting>
-1999-01-08 04:05:06 -8:00
-</programlisting>
-
- is a valid <type>timestamp</type> value that is <acronym>ISO</acronym>-compliant.
- In addition, the wide-spread format
-
-<programlisting>
-January 8 04:05:06 1999 PST
-</programlisting>
- is supported.
- </para>
-
- <para>
- The optional precision
- <replaceable>p</replaceable> should be between 0 and 13, and
- defaults to the precision of the input <type>timestamp</type> literal.
- </para>
- <para>
<table tocentry="1" id="datatype-timezone-table">
<title>Time Zone Input</title>
<tgroup cols="2">
</tbody>
</tgroup>
</table>
- </para>
</sect3>
<sect3>
- <title><type>interval [ ( <replaceable>precision</replaceable> ) ]</type></title>
+ <title>Intervals</title>
<indexterm>
<primary>interval</primary>
<para>
The optional precision
- <replaceable>p</replaceable> should be between 0 and 13, and
+ <replaceable>p</replaceable> should be between 0 and 6, and
defaults to the precision of the input literal.
</para>
</sect3>
input for the corresponding data type: <literal>CURRENT_DATE</literal>,
<literal>CURRENT_TIME</literal>,
<literal>CURRENT_TIMESTAMP</literal>. The latter two accept an
- optional precision specification.
+ optional precision specification. (See also <xref linkend="functions-datetime">.)
</para>
<para>
<productname>PostgreSQL</productname> also supports several
- special constants for convenience.
+ special constants for convenience, shown in <xref
+ linkend="datatype-datetime-special-table">.
+ </para>
- <table tocentry="1">
+ <table id="datatype-datetime-special-table">
<title>Special Date/Time Constants</title>
<tgroup cols="2">
<thead>
</row>
<row>
<entry><literal>infinity</literal></entry>
- <entry>Later than other valid times</entry>
+ <entry>later than other valid times</entry>
</row>
<row>
<entry><literal>-infinity</literal></entry>
- <entry>Earlier than other valid times</entry>
+ <entry>earlier than other valid times</entry>
</row>
<row>
<entry><literal>invalid</literal></entry>
- <entry>Illegal entry</entry>
+ <entry>illegal entry</entry>
</row>
<row>
<entry><literal>now</literal></entry>
- <entry>Current transaction time</entry>
+ <entry>current transaction time</entry>
</row>
<row>
<entry><literal>today</literal></entry>
- <entry>Midnight today</entry>
+ <entry>midnight today</entry>
</row>
<row>
<entry><literal>tomorrow</literal></entry>
- <entry>Midnight tomorrow</entry>
+ <entry>midnight tomorrow</entry>
</row>
<row>
<entry><literal>yesterday</literal></entry>
- <entry>Midnight yesterday</entry>
+ <entry>midnight yesterday</entry>
</row>
<row>
<entry><literal>zulu</>, <literal>allballs</>, <literal>z</></entry>
</tgroup>
</table>
- <literal>'now'</literal> is
- evaluated when the value is first interpreted.
- </para>
-
- <note>
- <para>
- As of <productname>PostgreSQL</> version 7.2,
- <literal>'current'</literal> is no longer supported as a
- date/time constant.
- Previously,
- <literal>'current'</literal> was stored as a special value,
- and evaluated to <literal>'now'</literal> only when
- used in an expression or type
- conversion.
- </para>
- </note>
</sect3>
</sect2>
</indexterm>
<para>
- Output formats can be set to one of the four styles
- ISO 8601, <acronym>SQL</acronym> (Ingres), traditional
- PostgreSQL, and German, using the <command>SET DateStyle</command>.
- The default is the <acronym>ISO</acronym> format.
+ Output formats can be set to one of the four styles ISO 8601,
+ <acronym>SQL</acronym> (Ingres), traditional PostgreSQL, and
+ German, using the <command>SET DateStyle</command>. The default
+ is the <acronym>ISO</acronym> format. (The SQL standard requires
+ the use of the ISO 8601 format. The name of the
+ <quote>SQL</quote> output format is a historical accident.)
+ <xref linkend="datatype-datetime-output-table"> shows examples of
+ each output style. The output of the <type>date</type> and
+ <type>time</type> types is of course only the date or time part
+ in accordance with the given examples.
+ </para>
- <table tocentry="1">
+ <table id="datatype-datetime-output-table">
<title>Date/Time Output Styles</title>
<tgroup cols="3">
<thead>
</thead>
<tbody>
<row>
- <entry>'ISO'</entry>
- <entry>ISO-8601 standard</entry>
+ <entry>ISO</entry>
+ <entry>ISO 8601/SQL standard</entry>
<entry>1997-12-17 07:37:16-08</entry>
</row>
<row>
- <entry>'SQL'</entry>
- <entry>Traditional style</entry>
+ <entry>SQL</entry>
+ <entry>traditional style</entry>
<entry>12/17/1997 07:37:16.00 PST</entry>
</row>
<row>
- <entry>'PostgreSQL'</entry>
- <entry>Original style</entry>
+ <entry>PostgreSQL</entry>
+ <entry>original style</entry>
<entry>Wed Dec 17 07:37:16 1997 PST</entry>
</row>
<row>
- <entry>'German'</entry>
- <entry>Regional style</entry>
+ <entry>German</entry>
+ <entry>regional style</entry>
<entry>17.12.1997 07:37:16.00 PST</entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
<para>
- The output of the <type>date</type> and <type>time</type> styles
- is of course
- only the date or time part in accordance with the above examples.
+ The <acronym>SQL</acronym> style has European and non-European
+ (U.S.) variants, which determines whether month follows day or
+ vice versa. (See <xref linkend="datatype-datetime-input">
+ for how this setting also affects interpretation of input values.)
+ <xref linkend="datatype-datetime-output2-table"> shows an
+ example.
</para>
- <para>
- The <acronym>SQL</acronym> style has European and non-European
- (U.S.) variants,
- which determines whether month follows day or vice versa. (See
- also <xref linkend="datatype-datetime-input">
- for how this setting affects interpretation of
- input values.)
-
- <table tocentry="1">
- <title>Date-Order Conventions</title>
+ <table id="datatype-datetime-output2-table">
+ <title>Date Order Conventions</title>
<tgroup cols="3">
<thead>
<row>
</tbody>
</tgroup>
</table>
- </para>
<para>
<type>interval</type> output looks like the input format, except that units like
</para>
<para>
- There are several ways to affect the appearance of date/time types:
-
- <itemizedlist spacing="compact" mark="bullet">
- <listitem>
- <para>
- The <envar>PGDATESTYLE</envar> environment variable used by the backend directly
- on postmaster start-up.
- </para>
- </listitem>
- <listitem>
- <para>
- The <envar>PGDATESTYLE</envar> environment variable used by the frontend <application>libpq</application>
- on session start-up.
- </para>
- </listitem>
- <listitem>
- <para>
- <command>SET DATESTYLE</command> <acronym>SQL</acronym> command.
- </para>
- </listitem>
- </itemizedlist>
+ The date/time styles can be selected by the user using the
+ <command>SET DATESTYLE</command> command, the
+ <varname>datestyle</varname> parameter in the
+ <filename>postgresql.conf</filename> configuration file, and the
+ <envar>PGDATESTYLE</envar> environment variable on the server or
+ client. The formatting function <function>to_char</function>
+ (see <xref linkend="functions-formatting">) is also available as
+ a more flexible way to format the date/time output.
</para>
-
</sect2>
<sect2 id="datatype-timezones">
<para>
<productname>PostgreSQL</productname> endeavors to be compatible with
- <acronym>SQL92</acronym> definitions for typical usage.
- However, the <acronym>SQL92</acronym> standard has an odd mix of date and
+ the <acronym>SQL</acronym> standard definitions for typical usage.
+ However, the <acronym>SQL</acronym> standard has an odd mix of date and
time types and capabilities. Two obvious problems are:
<itemizedlist>
<para>
To address these difficulties, we recommend using date/time
types that contain both date and time when using time zones. We
- recommend <emphasis>not</emphasis> using the SQL92 type <type>time
+ recommend <emphasis>not</emphasis> using the type <type>time
with time zone</type> (though it is supported by
<productname>PostgreSQL</productname> for legacy applications and
- for compatibility with other RDBMS implementations).
+ for compatibility with other SQL implementations).
<productname>PostgreSQL</productname>
assumes your local time zone for any type containing only
date or time. Further, time zone support is derived from
<para>
There are several ways to affect the time-zone behavior:
- <itemizedlist spacing="compact" mark="bullet">
+ <itemizedlist>
<listitem>
<para>
- The <envar>TZ</envar> environment variable is used by the backend directly
- on postmaster start-up as the default time zone.
+ The <envar>TZ</envar> environment variable on the server host
+ is used by the server as the default time zone.
</para>
</listitem>
+
<listitem>
<para>
- The <envar>PGTZ</envar> environment variable, if set at the client, is used by <application>libpq</application>
- to send a <command>SET TIME ZONE</command> command to the backend upon
- connection.
+ The <envar>PGTZ</envar> environment variable, if set at the
+ client, is used by <application>libpq</application>
+ applications to send a <command>SET TIME ZONE</command>
+ command to the server upon connection.
</para>
</listitem>
+
<listitem>
<para>
The <acronym>SQL</acronym> command <command>SET TIME ZONE</command>
sets the time zone for the session.
</para>
</listitem>
+
<listitem>
<para>
- The <acronym>SQL92</acronym> qualifier on
+ The construct
<programlisting>
<replaceable>timestamp</replaceable> AT TIME ZONE '<replaceable>zone</replaceable>'
</programlisting>
where <replaceable>zone</replaceable> can be specified as a
- text time zone (e.g. <literal>'PST'</literal>) or as an
- interval (e.g. <literal>INTERVAL '-08:00'</literal>).
+ text time zone (e.g., <literal>'PST'</literal>) or as an
+ interval (e.g., <literal>INTERVAL '-08:00'</literal>).
</para>
</listitem>
</itemizedlist>
</para>
</note>
- <note>
- <para>
- If the run-time option <literal>AUSTRALIAN_TIMEZONES</literal> is set
- then <literal>CST</literal> and <literal>EST</literal> refer to
- Australian time zones, not American ones.
- </para>
- </note>
+ <para>
+ Refer to <xref linkend="datetime-appendix"> for a list of
+ available time zones.
+ </para>
</sect2>
<para>
<productname>PostgreSQL</productname> uses Julian dates
for all date/time calculations. They have the nice property of correctly
- predicting/calculating any date more recent than 4713BC
+ predicting/calculating any date more recent than 4713 BC
to far into the future, using the assumption that the length of the
year is 365.2425 days.
</para>
<para>
<productname>PostgreSQL</productname> provides the
- <acronym>SQL99</acronym> type <type>boolean</type>.
+ standard <acronym>SQL</acronym> type <type>boolean</type>.
<type>boolean</type> can have one of only two states:
<quote>true</quote> or <quote>false</quote>. A third state,
<quote>unknown</quote>, is represented by the
- <acronym>SQL</acronym> NULL state.
+ <acronym>SQL</acronym> null value.
</para>
<para>
<title>Geometric Types</title>
<para>
- Geometric types represent two-dimensional spatial objects.
- The most fundamental type,
- the point, forms the basis for all of the other types.
+ Geometric data types represent two-dimensional spatial
+ objects. <xref linkend="datatype-geo-table"> shows the geometric
+ types available in PostgreSQL. The most fundamental type, the
+ point, forms the basis for all of the other types.
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-geo-table">
<title>Geometric Types</title>
<tgroup cols="4">
<thead>
</tbody>
</tgroup>
</table>
- </para>
<para>
A rich set of functions and operators is available to perform various geometric
operations such as scaling, translation, rotation, and determining
- intersections.
+ intersections. They are explained in <xref linkend="functions-geometry">.
</para>
<sect2>
<para>
Points are the fundamental two-dimensional building block for geometric types.
- </para>
-
- <para>
<type>point</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
( <replaceable>x</replaceable> , <replaceable>y</replaceable> )
<replaceable>x</replaceable> , <replaceable>y</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<term><replaceable>x</replaceable></term>
<listitem>
<para>
- The x-axis coordinate as a floating-point number
+ the x-axis coordinate as a floating-point number
</para>
</listitem>
</varlistentry>
<term><replaceable>y</replaceable></term>
<listitem>
<para>
- The y-axis coordinate as a floating-point number
+ the y-axis coordinate as a floating-point number
</para>
</listitem>
</varlistentry>
<para>
Line segments (<type>lseg</type>) are represented by pairs of points.
- </para>
-
- <para>
<type>lseg</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<term>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</term>
<listitem>
<para>
- The end points of the line segment
+ the end points of the line segment
</para>
</listitem>
</varlistentry>
<para>
Boxes are represented by pairs of points that are opposite
corners of the box.
- </para>
-
- <para>
<type>box</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> ) )
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ( <replaceable>x2</replaceable> , <replaceable>y2</replaceable> )
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , <replaceable>x2</replaceable> , <replaceable>y2</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<term>(<replaceable>x2</replaceable>,<replaceable>y2</replaceable>)</term>
<listitem>
<para>
- Opposite corners of the box
+ opposite corners of the box
</para>
</listitem>
</varlistentry>
The corners are reordered on input to store
the upper right corner, then the lower left corner.
Other corners of the box can be entered, but the lower
- left and upper right corners are determined from the input and stored.
+ left and upper right corners are determined from the input and stored corners.
</para>
</sect2>
<para>
<type>path</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
[ ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) ]
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<listitem>
<para>
End points of the line segments comprising the path.
- A leading square bracket ("[") indicates an open path, while
- a leading parenthesis ("(") indicates a closed path.
+ A leading square bracket (<literal>[</>) indicates an open path, while
+ a leading parenthesis (<literal>(</>) indicates a closed path.
</para>
</listitem>
</varlistentry>
<para>
<type>polygon</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
( ( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> ) )
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> ) , ... , ( <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
( <replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable> )
<replaceable>x1</replaceable> , <replaceable>y1</replaceable> , ... , <replaceable>xn</replaceable> , <replaceable>yn</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<para>
Circles are represented by a center point and a radius.
- </para>
-
- <para>
<type>circle</type> is specified using the following syntax:
- <synopsis>
+<synopsis>
< ( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable> >
( ( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable> )
( <replaceable>x</replaceable> , <replaceable>y</replaceable> ) , <replaceable>r</replaceable>
<replaceable>x</replaceable> , <replaceable>y</replaceable> , <replaceable>r</replaceable>
- </synopsis>
+</synopsis>
where the arguments are
<term>(<replaceable>x</replaceable>,<replaceable>y</replaceable>)</term>
<listitem>
<para>
- Center of the circle
+ center of the circle
</para>
</listitem>
</varlistentry>
<term><replaceable>r</replaceable></term>
<listitem>
<para>
- Radius of the circle
+ radius of the circle
</para>
</listitem>
</varlistentry>
<para>
<productname>PostgreSQL</> offers data types to store IP and MAC
- addresses. It is preferable to use these types over plain text
- types, because these types offer input error checking and several
- specialized operators and functions.
+ addresses, shown in <xref linkend="datatype-net-types-table">. It
+ is preferable to use these types over plain text types, because
+ these types offer input error checking and several specialized
+ operators and functions.
+ </para>
<table tocentry="1" id="datatype-net-types-table">
<title>Network Address Data Types</title>
</tbody>
</tgroup>
</table>
- </para>
<para>
- IP v6 is not yet supported.
+ IPv6 is not yet supported.
</para>
</para>
<para>
- Here are some examples:
+ <xref linkend="datatype-net-cidr-table"> shows some examples.
+ </para>
- <table tocentry="1">
+ <table id="datatype-net-cidr-table">
<title><type>cidr</> Type Input Examples</title>
<tgroup cols="3">
<thead>
</tbody>
</tgroup>
</table>
- </para>
</sect2>
<sect2 id="datatype-inet-vs-cidr">
Type <type>oid</> represents an object identifier. There are also
several aliases for <type>oid</>: <type>regproc</>, <type>regprocedure</>,
<type>regoper</>, <type>regoperator</>, <type>regclass</>,
- and <type>regtype</>.
+ and <type>regtype</>. <xref linkend="datatype-oid-table"> shows an overview.
</para>
<para>
types allow simplified lookup of OID values for objects: for example,
one may write <literal>'mytable'::regclass</> to get the OID of table
<literal>mytable</>, rather than <literal>SELECT oid FROM pg_class WHERE
- relname = 'mytable'</>. (In reality, a much more complicated SELECT would
+ relname = 'mytable'</>. (In reality, a much more complicated <command>SELECT</> would
be needed to deal with selecting the right OID when there are multiple
tables named <literal>mytable</> in different schemas.)
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-oid-table">
<title>Object Identifier Types</title>
<tgroup cols="4">
<thead>
<entry>Type name</entry>
<entry>References</entry>
<entry>Description</entry>
- <entry>Examples</entry>
+ <entry>Value example</entry>
</row>
</thead>
<row>
<entry><type>oid</></entry>
<entry>any</entry>
- <entry>Numeric object identifier</entry>
- <entry>564182</entry>
+ <entry>numeric object identifier</entry>
+ <entry><literal>564182</></entry>
</row>
<row>
<entry><type>regproc</></entry>
<entry><structname>pg_proc</></entry>
- <entry>Function name</entry>
- <entry>sum</entry>
+ <entry>function name</entry>
+ <entry><literal>sum</></entry>
</row>
<row>
<entry><type>regprocedure</></entry>
<entry><structname>pg_proc</></entry>
- <entry>Function with argument types</entry>
- <entry>sum(int4)</entry>
+ <entry>function with argument types</entry>
+ <entry><literal>sum(int4)</></entry>
</row>
<row>
<entry><type>regoper</></entry>
- <entry>pg_operator</entry>
- <entry>Operator name</entry>
- <entry>+</entry>
+ <entry><structname>pg_operator</></entry>
+ <entry>operator name</entry>
+ <entry><literal>+</></entry>
</row>
<row>
<entry><type>regoperator</></entry>
- <entry>pg_operator</entry>
- <entry>Operator with argument types</entry>
- <entry>*(integer,integer) -(NONE,integer)</entry>
+ <entry><structname>pg_operator</></entry>
+ <entry>operator with argument types</entry>
+ <entry><literal>*(integer,integer)</> or <literal>-(NONE,integer)</></entry>
</row>
<row>
<entry><type>regclass</></entry>
- <entry>pg_class</entry>
- <entry>Relation name</entry>
- <entry>pg_type</entry>
+ <entry><structname>pg_class</></entry>
+ <entry>relation name</entry>
+ <entry><literal>pg_type</></entry>
</row>
<row>
<entry><type>regtype</></entry>
- <entry>pg_type</entry>
- <entry>Type name</entry>
- <entry>integer</entry>
+ <entry><structname>pg_type</></entry>
+ <entry>type name</entry>
+ <entry><literal>integer</></entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
<para>
All of the OID alias types accept schema-qualified names, and will
accept input names that are unique (not overloaded), so they are
of limited use; for most uses <type>regprocedure</> or
<type>regoperator</> is more appropriate. For <type>regoperator</>,
- unary operators are identified by writing NONE for the unused
+ unary operators are identified by writing <literal>NONE</> for the unused
operand.
</para>
Transaction identifiers are 32-bit quantities. In a long-lived
database it is possible for transaction IDs to wrap around. This
is not a fatal problem given appropriate maintenance procedures;
- see the <citetitle>Administrator's Guide</> for details. However, it is
+ see the &cite-admin; for details. However, it is
unwise to depend on uniqueness of transaction IDs over the long term
(more than one billion transactions).
</para>
limit of 2<superscript>32</> (4 billion) SQL commands within a single
transaction.
In practice this limit is not a problem --- note that the limit is on
- number of SQL queries, not number of tuples processed.
+ number of SQL commands, not number of tuples processed.
</para>
<para>
</indexterm>
<para>
- The <productname>PostgreSQL</productname> type system contains a number
- of special-purpose entries that are collectively called
- <firstterm>pseudo-types</>. A pseudo-type cannot be used as a column
- data type, but it can be used to declare a function's argument or result
- type. Each of the available pseudo-types is useful in situations where
- a function's behavior does not correspond to simply taking or returning
- a value of a specific SQL data type.
+ The <productname>PostgreSQL</productname> type system contains a
+ number of special-purpose entries that are collectively called
+ <firstterm>pseudo-types</>. A pseudo-type cannot be used as a
+ column data type, but it can be used to declare a function's
+ argument or result type. Each of the available pseudo-types is
+ useful in situations where a function's behavior does not
+ correspond to simply taking or returning a value of a specific SQL
+ data type. <xref linkend="datatype-pseudotypes-table"> lists the
+ existing pseudo-types.
</para>
- <para>
- <table tocentry="1">
+ <table id="datatype-pseudotypes-table">
<title>Pseudo-Types</title>
<tgroup cols="2">
<thead>
<row>
<entry><type>record</></entry>
- <entry>Identifies a function returning an unspecified tuple type</entry>
+ <entry>Identifies a function returning an unspecified row type</entry>
</row>
<row>
</tbody>
</tgroup>
</table>
- </para>
<para>
Functions coded in C (whether built-in or dynamically loaded) may be
<productname>PostgreSQL</productname> provides a large number of
functions and operators for the built-in data types. Users can also
define their own functions and operators, as described in the
- <citetitle>Programmer's Guide</citetitle>. The
+ &cite-programmer;. The
<application>psql</application> commands <command>\df</command> and
<command>\do</command> can be used to show the list of all actually
available functions and operators, respectively.
and some explicitly marked functions, are not specified by the
<acronym>SQL</acronym>
standard. Some of this extended functionality is present in other
- <acronym>RDBMS</acronym> products, and in many cases this
+ <acronym>SQL</acronym> implementations, and in many cases this
functionality is compatible and consistent between various products.
</para>
<secondary>operators</secondary>
</indexterm>
- <table>
+ <para>
+ The usual comparison operators are available, shown in <xref
+ linkend="functions-comparison-table">.
+ </para>
+
+ <table id="functions-comparison-table">
<title>Comparison Operators</title>
<tgroup cols="2">
<thead>
</indexterm>
In addition to the comparison operators, the special
<token>BETWEEN</token> construct is available.
- <synopsis>
+<synopsis>
<replaceable>a</replaceable> BETWEEN <replaceable>x</replaceable> AND <replaceable>y</replaceable>
- </synopsis>
+</synopsis>
is equivalent to
- <synopsis>
+<synopsis>
<replaceable>a</replaceable> >= <replaceable>x</replaceable> AND <replaceable>a</replaceable> <= <replaceable>y</replaceable>
- </synopsis>
+</synopsis>
Similarly,
- <synopsis>
+<synopsis>
<replaceable>a</replaceable> NOT BETWEEN <replaceable>x</replaceable> AND <replaceable>y</replaceable>
- </synopsis>
+</synopsis>
is equivalent to
- <synopsis>
+<synopsis>
<replaceable>a</replaceable> < <replaceable>x</replaceable> OR <replaceable>a</replaceable> > <replaceable>y</replaceable>
- </synopsis>
+</synopsis>
There is no difference between the two respective forms apart from
the <acronym>CPU</acronym> cycles required to rewrite the first one
into the second one internally.
<para>
To check whether a value is or is not null, use the constructs
- <synopsis>
+<synopsis>
<replaceable>expression</replaceable> IS NULL
<replaceable>expression</replaceable> IS NOT NULL
- </synopsis>
- or the equivalent, but less standard, constructs
- <synopsis>
+</synopsis>
+ or the equivalent, but nonstandard, constructs
+<synopsis>
<replaceable>expression</replaceable> ISNULL
<replaceable>expression</replaceable> NOTNULL
- </synopsis>
+</synopsis>
</para>
<para>
<para>
Boolean values can also be tested using the constructs
- <synopsis>
+<synopsis>
<replaceable>expression</replaceable> IS TRUE
<replaceable>expression</replaceable> IS NOT TRUE
<replaceable>expression</replaceable> IS FALSE
<replaceable>expression</replaceable> IS NOT FALSE
<replaceable>expression</replaceable> IS UNKNOWN
<replaceable>expression</replaceable> IS NOT UNKNOWN
- </synopsis>
+</synopsis>
These are similar to <literal>IS NULL</literal> in that they will
always return true or false, never a null value, even when the operand is null.
A null input is treated as the logical value <quote>unknown</>.
Mathematical operators are provided for many
<productname>PostgreSQL</productname> types. For types without
common mathematical conventions for all possible permutations
- (e.g. date/time types) we
+ (e.g., date/time types) we
describe the actual behavior in subsequent sections.
</para>
- <table>
+ <para>
+ <xref linkend="functions-math-op-table"> shows the available mathematical operators.
+ </para>
+
+ <table id="functions-math-op-table">
<title>Mathematical Operators</title>
<tgroup cols="4">
<tbody>
<row>
<entry> <literal>+</literal> </entry>
- <entry>Addition</entry>
+ <entry>addition</entry>
<entry>2 + 3</entry>
<entry>5</entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
- <entry>Subtraction</entry>
+ <entry>subtraction</entry>
<entry>2 - 3</entry>
<entry>-1</entry>
</row>
<row>
<entry> <literal>*</literal> </entry>
- <entry>Multiplication</entry>
+ <entry>multiplication</entry>
<entry>2 * 3</entry>
<entry>6</entry>
</row>
<row>
<entry> <literal>/</literal> </entry>
- <entry>Division (integer division truncates results)</entry>
+ <entry>division (integer division truncates results)</entry>
<entry>4 / 2</entry>
<entry>2</entry>
</row>
<row>
<entry> <literal>%</literal> </entry>
- <entry>Modulo (remainder)</entry>
+ <entry>modulo (remainder)</entry>
<entry>5 % 4</entry>
<entry>1</entry>
</row>
<row>
<entry> <literal>^</literal> </entry>
- <entry>Exponentiation</entry>
+ <entry>exponentiation</entry>
<entry>2.0 ^ 3.0</entry>
<entry>8</entry>
</row>
<row>
<entry> <literal>|/</literal> </entry>
- <entry>Square root</entry>
+ <entry>square root</entry>
<entry>|/ 25.0</entry>
<entry>5</entry>
</row>
<row>
<entry> <literal>||/</literal> </entry>
- <entry>Cube root</entry>
+ <entry>cube root</entry>
<entry>||/ 27.0</entry>
<entry>3</entry>
</row>
<row>
<entry> <literal>!</literal> </entry>
- <entry>Factorial</entry>
+ <entry>factorial</entry>
<entry>5 !</entry>
<entry>120</entry>
</row>
<row>
<entry> <literal>!!</literal> </entry>
- <entry>Factorial (prefix operator)</entry>
+ <entry>factorial (prefix operator)</entry>
<entry>!! 5</entry>
<entry>120</entry>
</row>
<row>
<entry> <literal>@</literal> </entry>
- <entry>Absolute value</entry>
+ <entry>absolute value</entry>
<entry>@ -5.0</entry>
<entry>5</entry>
</row>
<row>
<entry> <literal>&</literal> </entry>
- <entry>Binary AND</entry>
+ <entry>binary AND</entry>
<entry>91 & 15</entry>
<entry>11</entry>
</row>
<row>
<entry> <literal>|</literal> </entry>
- <entry>Binary OR</entry>
+ <entry>binary OR</entry>
<entry>32 | 3</entry>
<entry>35</entry>
</row>
<row>
<entry> <literal>#</literal> </entry>
- <entry>Binary XOR</entry>
+ <entry>binary XOR</entry>
<entry>17 # 5</entry>
<entry>20</entry>
</row>
<row>
<entry> <literal>~</literal> </entry>
- <entry>Binary NOT</entry>
+ <entry>binary NOT</entry>
<entry>~1</entry>
<entry>-2</entry>
</row>
<row>
<entry> << </entry>
- <entry>Binary shift left</entry>
+ <entry>binary shift left</entry>
<entry>1 << 4</entry>
<entry>16</entry>
</row>
<row>
<entry> >> </entry>
- <entry>Binary shift right</entry>
+ <entry>binary shift right</entry>
<entry>8 >> 2</entry>
<entry>2</entry>
</row>
<para>
The <quote>binary</quote> operators are also available for the bit
- string types <type>BIT</type> and <type>BIT VARYING</type>.
+ string types <type>BIT</type> and <type>BIT VARYING</type>, as
+ shown in <xref linkend="functions-math-bit-table">.
+ Bit string arguments to <literal>&</literal>, <literal>|</literal>,
+ and <literal>#</literal> must be of equal length. When bit
+ shifting, the original length of the string is preserved, as shown in the table.
+ </para>
- <table>
+ <table id="functions-math-bit-table">
<title>Bit String Binary Operators</title>
<tgroup cols="2">
</tgroup>
</table>
- Bit string arguments to <literal>&</literal>, <literal>|</literal>,
- and <literal>#</literal> must be of equal length. When bit
- shifting, the original length of the string is preserved, as shown
- here.
- </para>
+ <para>
+ <xref linkend="functions-math-func-table"> shows the available
+ mathematical functions. In the table, <literal>dp</literal>
+ indicates <type>double precision</type>. The functions
+ <function>exp</function>, <function>ln</function>,
+ <function>log</function>, <function>pow</function>,
+ <function>round</function> (1 argument), <function>sqrt</function>,
+ and <function>trunc</function> (1 argument) are also available for
+ the type <type>numeric</type> in place of <type>double
+ precision</type>. Functions returning a <type>numeric</type>
+ result take <type>numeric</type> input arguments, unless otherwise
+ specified. Many of these functions are implemented on top of the
+ host system's C library; accuracy and behavior in boundary cases
+ could therefore vary depending on the host system.
+ </para>
- <table tocentry="1">
+ <table id="functions-math-func-table">
<title>Mathematical Functions</title>
<tgroup cols="5">
<thead>
<tbody>
<row>
<entry><function>abs</function>(<replaceable>x</replaceable>)</entry>
- <entry>(same as x)</entry>
+ <entry>(same as <replaceable>x</>)</entry>
<entry>absolute value</entry>
<entry><literal>abs(-17.4)</literal></entry>
<entry>17.4</entry>
</tgroup>
</table>
- <para>
- In the table above, <literal>dp</literal> indicates <type>double precision</type>.
- The functions <function>exp</function>, <function>ln</function>,
- <function>log</function>, <function>pow</function>,
- <function>round</function> (1 argument), <function>sqrt</function>,
- and <function>trunc</function> (1 argument) are also available for
- the type <type>numeric</type> in place of
- <type>double precision</type>.
- Functions returning a <type>numeric</type> result take
- <type>numeric</type> input arguments, unless otherwise specified.
- Many of these functions are implemented on top
- of the host system's C library; accuracy and behavior in boundary cases
- could therefore vary depending on the host system.
- </para>
+ <para>
+ Finally, <xref linkend="functions-math-trig-table"> shows the
+ available trigonometric functions. All trigonometric functions
+ have arguments and return values of type <type>double
+ precision</type>.
+ </para>
- <table>
+ <table id="functions-math-trig-table">
<title>Trigonometric Functions</title>
<tgroup cols="2">
</tgroup>
</table>
- <para>
- All trigonometric functions have arguments and return values of
- type <type>double precision</type>.
- </para>
-
</sect1>
<para>
<acronym>SQL</acronym> defines some string functions with a special syntax where
- certain keywords rather than commas are used to separate the
+ certain key words rather than commas are used to separate the
arguments. Details are in <xref linkend="functions-string-sql">.
These functions are also implemented using the regular syntax for
function invocation. (See <xref linkend="functions-string-other">.)
<parameter>string</parameter> </entry>
<entry> <type>text</type> </entry>
<entry>
- string concatenation
+ String concatenation
<indexterm>
<primary>character strings</primary>
<secondary>concatenation</secondary>
</indexterm>
</entry>
- <entry><literal>'Postgre' || 'SQL'</literal></entry>
+ <entry><literal>'Post' || 'greSQL'</literal></entry>
<entry><literal>PostgreSQL</literal></entry>
</row>
<row>
<entry><function>bit_length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
- <entry>number of bits in string</entry>
+ <entry>Number of bits in string</entry>
<entry><literal>bit_length('jose')</literal></entry>
<entry><literal>32</literal></entry>
</row>
<entry><function>char_length</function>(<parameter>string</parameter>) or <function>character_length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
<entry>
- number of characters in string
+ Number of characters in string
<indexterm>
<primary>character strings</primary>
<secondary>length</secondary>
names.
</entry>
<entry><literal>convert('PostgreSQL' using iso_8859_1_to_utf_8)</literal></entry>
- <entry><literal>'PostgreSQL'</literal> in UNICODE (UTF-8) encoding</entry>
+ <entry><literal>'PostgreSQL'</literal> in Unicode (UTF-8) encoding</entry>
</row>
<row>
<entry><function>lower</function>(<parameter>string</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Convert string to lower case.</entry>
+ <entry>Convert string to lower case</entry>
<entry><literal>lower('TOM')</literal></entry>
<entry><literal>tom</literal></entry>
</row>
<row>
<entry><function>octet_length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
- <entry>number of bytes in string</entry>
+ <entry>Number of bytes in string</entry>
<entry><literal>octet_length('jose')</literal></entry>
<entry><literal>4</literal></entry>
</row>
<entry><function>overlay</function>(<parameter>string</parameter> placing <parameter>string</parameter> from <type>integer</type> <optional>for <type>integer</type></optional>)</entry>
<entry><type>text</type></entry>
<entry>
- insert substring
+ Insert substring
<indexterm>
<primary>overlay</primary>
</indexterm>
<row>
<entry><function>position</function>(<parameter>substring</parameter> in <parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
- <entry>location of specified substring</entry>
+ <entry>Location of specified substring</entry>
<entry><literal>position('om' in 'Thomas')</literal></entry>
<entry><literal>3</literal></entry>
</row>
<entry><function>substring</function>(<parameter>string</parameter> <optional>from <type>integer</type></optional> <optional>for <type>integer</type></optional>)</entry>
<entry><type>text</type></entry>
<entry>
- extract substring
+ Extract substring
<indexterm>
<primary>substring</primary>
</indexterm>
<entry><function>substring</function>(<parameter>string</parameter> from <replaceable>pattern</replaceable>)</entry>
<entry><type>text</type></entry>
<entry>
- extract substring matching POSIX regular expression
+ Extract substring matching POSIX regular expression
<indexterm>
<primary>substring</primary>
</indexterm>
<entry><function>substring</function>(<parameter>string</parameter> from <replaceable>pattern</replaceable> for <replaceable>escape</replaceable>)</entry>
<entry><type>text</type></entry>
<entry>
- extract substring matching SQL99 regular expression
+ Extract substring matching SQL regular expression
<indexterm>
<primary>substring</primary>
</indexterm>
</entry>
<entry><type>text</type></entry>
<entry>
- Removes the longest string containing only the
+ Remove the longest string containing only the
<parameter>characters</parameter> (a space by default) from the
- beginning/end/both ends of the <parameter>string</parameter>.
+ beginning/end/both ends of the <parameter>string</parameter>
</entry>
<entry><literal>trim(both 'x' from 'xTomxx')</literal></entry>
<entry><literal>Tom</literal></entry>
<row>
<entry><function>upper</function>(<parameter>string</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Convert string to upper case.</entry>
+ <entry>Convert string to upper case</entry>
<entry><literal>upper('tom')</literal></entry>
<entry><literal>TOM</literal></entry>
</row>
<para>
Additional string manipulation functions are available and are
- listed below. Some of them are used internally to implement the
- <acronym>SQL</acronym>-standard string functions listed above.
+ listed in <xref linkend="functions-string-other">. Some of them are used internally to implement the
+ <acronym>SQL</acronym>-standard string functions listed in <xref linkend="functions-string-sql">.
</para>
<table id="functions-string-other">
<row>
<entry><function>ascii</function>(<type>text</type>)</entry>
<entry>integer</entry>
- <entry>
Returns the <acronym>ASCII</acronym> code of the first character of the argument.</entry>
+ <entry><acronym>ASCII</acronym> code of the first character of the argument.</entry>
<entry><literal>ascii('x')</literal></entry>
<entry><literal>120</literal></entry>
</row>
<entry>
Remove (trim) the longest string consisting only of characters
in <parameter>trim</parameter> from the start and end of
- <parameter>string</parameter>.
+ <parameter>string</parameter>
</entry>
<entry><literal>btrim('xyxtrimyyx','xy')</literal></entry>
<entry><literal>trim</literal></entry>
<row>
<entry><function>chr</function>(<type>integer</type>)</entry>
<entry><type>text</type></entry>
- <entry>Returns the character with the given <acronym>ASCII</acronym> code.</entry>
+ <entry>Character with the given <acronym>ASCII</acronym> code</entry>
<entry><literal>chr(65)</literal></entry>
<entry><literal>A</literal></entry>
</row>
</entry>
<entry><type>text</type></entry>
<entry>
- Convert
s string using <parameter>dest_encoding</parameter>.
+ Convert
string to <parameter>dest_encoding</parameter>.
The original encoding is specified by
<parameter>src_encoding</parameter>. If
<parameter>src_encoding</parameter> is omitted, database
</entry>
<entry><type>bytea</type></entry>
<entry>
- Decode
s binary data from <parameter>string</parameter> previously
- encoded with encode(). Parameter type is same as in encode().
+ Decode binary data from <parameter>string</parameter> previously
+ encoded with <function>encode()</>. Parameter type is same as in <function>encode()</>.
</entry>
<entry><literal>decode('MTIzAAE=', 'base64')</literal></entry>
<entry><literal>123\000\001</literal></entry>
</entry>
<entry><type>text</type></entry>
<entry>
- Encode
s binary data to <acronym>ASCII</acronym>-only representation. Supported
- types are: 'base64', 'hex', 'escape'.
+ Encode binary data to <acronym>ASCII</acronym>-only representation. Supported
+ types are: base64, hex, escape.
</entry>
<entry><literal>encode('123\\000\\001', 'base64')</literal></entry>
<entry><literal>MTIzAAE=</literal></entry>
<row>
<entry><function>initcap</function>(<type>text</type>)</entry>
<entry><type>text</type></entry>
- <entry>Converts first letter of each word (whitespace separated) to upper case.</entry>
+ <entry>Convert first letter of each word (whitespace separated) to upper case</entry>
<entry><literal>initcap('hi thomas')</literal></entry>
<entry><literal>Hi Thomas</literal></entry>
</row>
<entry><function>length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
<entry>
- length of string
+ Length of string
<indexterm>
<primary>character strings</primary>
<secondary>length</secondary>
</entry>
<entry>text</entry>
<entry>
- Fill
s up the <parameter>string</parameter> to length
+ Fill up the <parameter>string</parameter> to length
<parameter>length</parameter> by prepending the characters
<parameter>fill</parameter> (a space by default). If the
<parameter>string</parameter> is already longer than
<entry><function>ltrim</function>(<parameter>string</parameter> <type>text</type>, <parameter>text</parameter> <type>text</type>)</entry>
<entry><type>text</type></entry>
<entry>
- Removes the longest string containing only characters from
+ Remove the longest string containing only characters from
<parameter>trim</parameter> from the start of the string.
</entry>
<entry><literal>ltrim('zzzytrim','xyz')</literal></entry>
<entry><function>pg_client_encoding</function>()</entry>
<entry><type>name</type></entry>
<entry>
- Returns current client encoding name.
+ Current client encoding name.
</entry>
<entry><literal>pg_client_encoding()</literal></entry>
<entry><literal>SQL_ASCII</literal></entry>
<entry><function>quote_ident</function>(<parameter>string</parameter> text)</entry>
<entry><type>text</type></entry>
<entry>
- Returns the given string suitably quoted to be used as an identifier
+ Return the given string suitably quoted to be used as an identifier
in an SQL query string.
Quotes are added only if necessary (i.e., if the string contains
non-identifier characters or would be case-folded).
<entry><function>quote_literal</function>(<parameter>string</parameter> text)</entry>
<entry><type>text</type></entry>
<entry>
- Returns the given string suitably quoted to be used as a literal
+ Return the given string suitably quoted to be used as a literal
in an SQL query string.
Embedded quotes and backslashes are properly doubled.
</entry>
<row>
<entry><function>repeat</function>(<type>text</type>, <type>integer</type>)</entry>
<entry><type>text</type></entry>
- <entry>Repeat text a number of times.</entry>
+ <entry>Repeat text a number of times</entry>
<entry><literal>repeat('Pg', 4)</literal></entry>
<entry><literal>PgPgPgPg</literal></entry>
</row>
</entry>
<entry><type>text</type></entry>
<entry>
- Fill
s up the <parameter>string</parameter> to length
+ Fill up the <parameter>string</parameter> to length
<parameter>length</parameter> by appending the characters
<parameter>fill</parameter> (a space by default). If the
<parameter>string</parameter> is already longer than
text, <parameter>trim</parameter> text)</entry>
<entry><type>text</type></entry>
<entry>
- Removes the longest string containing only characters from
+ Remove the longest string containing only characters from
<parameter>trim</parameter> from the end of the string.
</entry>
<entry><literal>rtrim('trimxxxx','x')</literal></entry>
<entry><function>strpos</function>(<parameter>string</parameter>, <parameter>substring</parameter>)</entry>
<entry><type>text</type></entry>
<entry>
- Locates specified substring. (same as
+ Locate specified substring (same as
<literal>position(<parameter>substring</parameter> in
<parameter>string</parameter>)</literal>, but note the reversed
argument order)
<entry><function>substr</function>(<parameter>string</parameter>, <parameter>from</parameter> <optional>, <parameter>count</parameter></optional>)</entry>
<entry><type>text</type></entry>
<entry>
- Extracts specified substring. (same as
+ Extract specified substring (same as
<literal>substring(<parameter>string</parameter> from <parameter>from</parameter> for <parameter>count</parameter>)</literal>)
</entry>
<entry><literal>substr('alphabet', 3, 2)</literal></entry>
<entry><function>to_ascii</function>(<type>text</type>
<optional>, <parameter>encoding</parameter></optional>)</entry>
<entry><type>text</type></entry>
- <entry>Converts text from multibyte encoding to <acronym>ASCII</acronym>.</entry>
+
+ <entry>
+ Convert text to <acronym>ASCII</acronym> from other encoding
+ <footnote>
+ <para>
+ The <function>to_ascii</function> function supports conversion from
+ <literal>LATIN1</>, <literal>LATIN2</>, and <literal>WIN1250</> only.
+ </para>
+ </footnote>
+ </entry>
+
<entry><literal>to_ascii('Karel')</literal></entry>
<entry><literal>Karel</literal></entry>
</row>
or <type>bigint</type>)</entry>
<entry><type>text</type></entry>
<entry>Convert <parameter>number</parameter> to its equivalent hexadecimal
- representation.
+ representation
</entry>
<entry><literal>to_hex(9223372036854775807::bigint)</literal></entry>
<entry><literal>7fffffffffffffff</literal></entry>
</tgroup>
</table>
- <para>
- The <function>to_ascii</function> function supports conversion from
- <literal>LATIN1</>, <literal>LATIN2</>, and <literal>WIN1250</> only.
- </para>
-
<table id="conversion-names">
<title>Built-in Conversions</title>
<para>
<acronym>SQL</acronym> defines some string functions with a
special syntax where
- certain keywords rather than commas are used to separate the
+ certain key words rather than commas are used to separate the
arguments. Details are in
<xref linkend="functions-binarystring-sql">.
Some functions are also implemented using the regular syntax for
<parameter>string</parameter> </entry>
<entry> <type>bytea</type> </entry>
<entry>
- string concatenation
+ String concatenation
<indexterm>
<primary>binary strings</primary>
<secondary>concatenation</secondary>
</indexterm>
</entry>
- <entry><literal>'\\\\Postgre'::bytea || '\\047SQL\\000'::bytea</literal></entry>
- <entry><literal>\\Postgre'SQL\000</literal></entry>
+ <entry><literal>'\\\\Post'::bytea || '\\047greSQL\\000'::bytea</literal></entry>
+ <entry><literal>\\Post'greSQL\000</literal></entry>
</row>
<row>
<entry><function>octet_length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
- <entry>number of bytes in binary string</entry>
+ <entry>Number of bytes in binary string</entry>
<entry><literal>octet_length('jo\\000se'::bytea)</literal></entry>
<entry><literal>5</literal></entry>
</row>
<row>
<entry><function>position</function>(<parameter>substring</parameter> in <parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
- <entry>location of specified substring</entry>
+ <entry>Location of specified substring</entry>
<entry><literal>position('\\000om'::bytea in 'Th\\000omas'::bytea)</literal></entry>
<entry><literal>3</literal></entry>
</row>
<entry><function>substring</function>(<parameter>string</parameter> <optional>from <type>integer</type></optional> <optional>for <type>integer</type></optional>)</entry>
<entry><type>bytea</type></entry>
<entry>
- extract substring
+ Extract substring
<indexterm>
<primary>substring</primary>
</indexterm>
</entry>
<entry><type>bytea</type></entry>
<entry>
- Removes the longest string containing only the
+ Remove the longest string containing only the
<parameter>characters</parameter> from the
- beginning/end/both ends of the <parameter>string</parameter>.
+ beginning/end/both ends of the <parameter>string</parameter>
</entry>
<entry><literal>trim('\\000'::bytea from '\\000Tom\\000'::bytea)</literal></entry>
<entry><literal>Tom</literal></entry>
</table>
<para>
- Additional binary string manipulation functions are available and are
- listed below. Some of them are used internally to implement the
- <acronym>SQL</acronym>-standard string functions listed above.
+ Additional binary string manipulation functions are available and
+ are listed in <xref linkend="functions-binarystring-other">. Some
+ of them are used internally to implement the
+ <acronym>SQL</acronym>-standard string functions listed in <xref
+ linkend="functions-binarystring-sql">.
</para>
<table id="functions-binarystring-other">
<entry><function>length</function>(<parameter>string</parameter>)</entry>
<entry><type>integer</type></entry>
<entry>
- length of binary string
+ Length of binary string
<indexterm>
<primary>binary strings</primary>
<secondary>length</secondary>
</entry>
<entry><type>text</type></entry>
<entry>
- Encode
s binary string to <acronym>ASCII</acronym>-only representation. Supported
- types are: 'base64', 'hex', 'escape'.
+ Encode binary string to <acronym>ASCII</acronym>-only representation. Supported
+ types are: base64, hex, escape.
</entry>
<entry><literal>encode('123\\000456'::bytea, 'escape')</literal></entry>
<entry><literal>123\000456</literal></entry>
</entry>
<entry><type>bytea</type></entry>
<entry>
- Decode
s binary string from <parameter>string</parameter> previously
- encoded with encode(). Parameter type is same as in encode().
+ Decode binary string from <parameter>string</parameter> previously
+ encoded with <literal>encode()</>. Parameter type is same as in <literal>encode()</>.
</entry>
<entry><literal>decode('123\\000456', 'escape')</literal></entry>
<entry><literal>123\000456</literal></entry>
<primary>like</primary>
</indexterm>
- <synopsis>
+<synopsis>
<replaceable>string</replaceable> LIKE <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
<replaceable>string</replaceable> NOT LIKE <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
- </synopsis>
+</synopsis>
<para>
Every <replaceable>pattern</replaceable> defines a set of strings.
of zero or more characters.
</para>
- <informalexample>
- <para>
- Some examples:
- <programlisting>
+ <para>
+ Some examples:
+<programlisting>
'abc' LIKE 'abc' <lineannotation>true</lineannotation>
'abc' LIKE 'a%' <lineannotation>true</lineannotation>
'abc' LIKE '_b_' <lineannotation>true</lineannotation>
'abc' LIKE 'c' <lineannotation>false</lineannotation>
- </programlisting>
- </para>
- </informalexample>
-
+</programlisting>
+ </para>
+
<para>
<function>LIKE</function> pattern matches always cover the entire
string. To match a pattern anywhere within a string, the
<primary>substring</primary>
</indexterm>
- <synopsis>
+<synopsis>
<replaceable>string</replaceable> SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
<replaceable>string</replaceable> NOT SIMILAR TO <replaceable>pattern</replaceable> <optional>ESCAPE <replaceable>escape-character</replaceable></optional>
- </synopsis>
+</synopsis>
<para>
The <function>SIMILAR TO</function> operator returns true or false
be specified with <literal>ESCAPE</>.
</para>
- <informalexample>
- <para>
- Some examples:
- <programlisting>
+ <para>
+ Some examples:
+<programlisting>
'abc' SIMILAR TO 'abc' <lineannotation>true</lineannotation>
'abc' SIMILAR TO 'a' <lineannotation>false</lineannotation>
'abc' SIMILAR TO '%(b|d)%' <lineannotation>true</lineannotation>
'abc' SIMILAR TO '(b|c)%' <lineannotation>false</lineannotation>
- </programlisting>
- </para>
- </informalexample>
+</programlisting>
+ </para>
<para>
- The SUBSTRING function with three parameters,
- <function>SUBSTRING
</function>(<parameter>string</parameter> FROM
+ The <function>SUBSTRING</> function with three parameters,
+ <function>SUBSTRING(<parameter>string</parameter> FROM
<replaceable>pattern</replaceable> FOR
- <replaceable>escape</replaceable>), provides extraction of a substring
- that matches a SQL99 regular expression pattern. As with SIMILAR TO,
- the specified pattern must match to the entire data string, else the
- function fails and returns NULL. To indicate the part of the pattern
- that should be returned on success, SQL99 specifies that the pattern
- must contain two occurrences of the escape character followed by
- double quote (<literal>"</>). The text matching the portion of the
- pattern between these markers is returned.
+ <replaceable>escape</replaceable>)</function>, provides
+ extraction of a substring that matches a SQL99 regular expression
+ pattern. As with <literal>SIMILAR TO</>, the specified pattern
+ must match to the entire data string, else the function fails and
+ returns null. To indicate the part of the pattern that should be
+ returned on success, SQL99 specifies that the pattern must
+ contain two occurrences of the escape character followed by
+ double quote (<literal>"</>). The text matching the portion of
+ the pattern between these markers is returned.
</para>
- <informalexample>
- <para>
- Some examples:
- <programlisting>
+ <para>
+ Some examples:
+<programlisting>
SUBSTRING('foobar' FROM '%#"o_b#"%' FOR '#') <lineannotation>oob</lineannotation>
SUBSTRING('foobar' FROM '#"o_b#"%' FOR '#') <lineannotation>NULL</lineannotation>
- </programlisting>
- </para>
- </informalexample>
-
+</programlisting>
+ </para>
</sect2>
<sect2 id="functions-posix-regexp">
<seealso>pattern matching</seealso>
</indexterm>
- <table>
+ <para>
+ <xref linkend="functions-posix-table"> lists the available
+ operators for pattern matching using POSIX regular expressions.
+ </para>
+
+ <table id="functions-posix-table">
<title>Regular Expression Match Operators</title>
<tgroup cols="3">
end of the string.
</para>
- <informalexample>
- <para>
- Some examples:
- <programlisting>
+ <para>
+ Some examples:
+<programlisting>
'abc' ~ 'abc' <lineannotation>true</lineannotation>
'abc' ~ '^a' <lineannotation>true</lineannotation>
'abc' ~ '(b|d)' <lineannotation>true</lineannotation>
'abc' ~ '^(b|c)' <lineannotation>false</lineannotation>
- </programlisting>
- </para>
- </informalexample>
+</programlisting>
+ </para>
<para>
- The SUBSTRING function with two parameters,
- <function>SUBSTRING
</function>(<parameter>string</parameter> FROM
- <replaceable>pattern</replaceable>), provides extraction of a substring
- that matches a POSIX regular expression pattern. It returns NULL if
+ The <function>SUBSTRING</> function with two parameters,
+ <function>SUBSTRING(<parameter>string</parameter> FROM
+ <replaceable>pattern</replaceable>)</function>, provides extraction of a substring
+ that matches a POSIX regular expression pattern. It returns null if
there is no match, otherwise the portion of the text that matched the
pattern. But if the pattern contains any parentheses, the portion
of the text that matched the first parenthesized subexpression (the
exception.
</para>
- <informalexample>
- <para>
- Some examples:
- <programlisting>
+ <para>
+ Some examples:
+<programlisting>
SUBSTRING('foobar' FROM 'o.b') <lineannotation>oob</lineannotation>
SUBSTRING('foobar' FROM 'o(.)b') <lineannotation>o</lineannotation>
- </programlisting>
- </para>
- </informalexample>
+</programlisting>
+ </para>
<!-- derived from the re_format.7 man page -->
<para>
<primary>formatting</primary>
</indexterm>
- <note>
- <title>Author</title>
- <para>
- </para>
- </note>
-
<para>
The <productname>PostgreSQL</productname> formatting functions
provide a powerful set of tools for converting various data types
(date/time, integer, floating point, numeric) to formatted strings
and for converting from formatted strings to specific data types.
+ <xref linkend="functions-formatting-table"> lists them.
These functions all follow a common calling convention: the first
argument is the value to be formatted and the second argument is a
template that defines the output or input format.
</para>
- <table tocentry="1">
+ <table id="functions-formatting-table">
<title>Formatting Functions</title>
<tgroup cols="4">
<thead>
<row>
<entry><function>to_char</function>(<type>int</type>, <type>text</type>)</entry>
<entry><type>text</type></entry>
- <entry>convert int4/int8 to string</entry>
+ <entry>convert integer to string</entry>
<entry><literal>to_char(125, '999')</literal></entry>
</row>
<row>
values to be found there.
</para>
- <table tocentry="1">
+ <para>
+ <xref linkend="functions-formatting-datetime-table"> shows the
+ template patterns available for formatting date and time values.
+ </para>
+
+ <table id="functions-formatting-datetime-table">
<title>Template patterns for date/time conversions</title>
<tgroup cols="2">
<thead>
</row>
<row>
<entry><literal>TZ</literal></entry>
- <entry>timezone name - upper case</entry>
+ <entry>time-zone name - upper case</entry>
</row>
<row>
<entry><literal>tz</literal></entry>
- <entry>timezone name - lower case</entry>
+ <entry>time-zone name - lower case</entry>
</row>
</tbody>
</tgroup>
behavior. For example, <quote><literal>FMMonth</literal></quote>
is the <quote><literal>Month</literal></quote> pattern with the
<quote><literal>FM</literal></quote> prefix.
+ <xref linkend="functions-formatting-datetimemod-table"> shows the
+ modifier patterns for date/time formatting.
</para>
- <table tocentry="1">
+ <table id="functions-formatting-datetimemod-table">
<title>Template pattern modifiers for date/time conversions</title>
<tgroup cols="3">
<thead>
</row>
<row>
<entry><literal>FX</literal> prefix</entry>
- <entry>Fixed format global option (see below)</entry>
+ <entry>fixed format global option (see usage notes)</entry>
<entry><literal>FX Month DD Day</literal></entry>
</row>
<row>
</table>
<para>
- Usage notes:
+ Usage notes for the date/time formatting:
<itemizedlist>
<listitem>
<para>
- <literal>FM</literal> suppresses leading zeroes or trailing blanks
+ <literal>FM</literal> suppresses leading zeroes and trailing blanks
that would otherwise be added to make the output of a pattern be
fixed-width.
</para>
templates and will be output literally. You can put a substring
in double quotes to force it to be interpreted as literal text
even if it contains pattern keywords. For example, in
- <literal>'"Hello Year: "YYYY'</literal>, the <literal>YYYY</literal>
- will be replaced by year data, but the single <literal>Y</literal>
+ <literal>'"Hello Year "YYYY'</literal>, the <literal>YYYY</literal>
+ will be replaced by the year data, but the single <literal>Y</literal> in <quote>Year</quote>
will not be.
</para>
</listitem>
</itemizedlist>
</para>
- <table tocentry="1">
+ <para>
+ <xref linkend="functions-formatting-numeric-table"> shows the
+ template patterns available for formatting numeric values.
+ </para>
+
+ <table id="functions-formatting-numeric-table">
<title>Template patterns for numeric conversions</title>
<tgroup cols="2">
<thead>
</table>
<para>
- Usage notes:
+ Usage notes for the numeric formatting:
<itemizedlist>
<listitem>
<para>
<literal>9</literal> specifies a value with the same number of
digits as there are <literal>9</literal>s. If a digit is
- not available use blank space.
+ not available it outputs a space.
</para>
</listitem>
</itemizedlist>
</para>
- <table tocentry="1">
+ <para>
+ <xref linkend="functions-formatting-examples-table"> shows some
+ examples of the use of the <function>to_char</function> function.
+ </para>
+
+ <table id="functions-formatting-examples-table">
<title><function>to_char</function> Examples</title>
<tgroup cols="2">
<thead>
<sect1 id="functions-datetime">
<title>Date/Time Functions and Operators</title>
- <para>
- <xref linkend="functions-datetime-table"> shows the available
- functions for date/time value processing.
- <xref linkend="operators-datetime-table"> illustrates the
- behaviors of the basic arithmetic
- operators (<literal>+</literal>, <literal>*</literal>, etc.).
- For formatting functions, refer to <xref
- linkend="functions-formatting">. You should be familiar with the
- background information on date/time data types (see <xref
- linkend="datatype-datetime">).
- </para>
-
- <para>
- The date/time operators described below behave similarly for types
- involving time zones as well as those without.
+ <para>
+ <xref linkend="functions-datetime-table"> shows the available
+ functions for date/time value processing, with details appearing in
+ the following subsections. <xref
+ linkend="operators-datetime-table"> illustrates the behaviors of
+ the basic arithmetic operators (<literal>+</literal>,
+ <literal>*</literal>, etc.). For formatting functions, refer to
+ <xref linkend="functions-formatting">. You should be familiar with
+ the background information on date/time data types (see <xref
+ linkend="datatype-datetime">). The date/time operators described
+ below behave similarly for types involving time zones as well as
+ those without.
+ </para>
<table id="operators-datetime-table">
<title>Date/Time Operators</title>
<tbody>
<row>
<entry> <literal>+</literal> </entry>
- <entry><type>timestamp</type> '2001-09-28 01:00' + <type>interval</type> '23 hours'</entry>
- <entry><type>timestamp</type> '2001-09-29 00:00'</entry>
+ <entry><literal>timestamp '2001-09-28 01:00' + interval '23 hours'</literal></entry>
+ <entry><literal>timestamp '2001-09-29 00:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
- <entry><type>date</type> '2001-09-28' + <type>interval</type> '1 hour'</entry>
- <entry><type>timestamp</type> '2001-09-28 01:00'</entry>
+ <entry><literal>date '2001-09-28' + interval '1 hour'</literal></entry>
+ <entry><literal>timestamp '2001-09-28 01:00'</literal></entry>
</row>
<row>
<entry> <literal>+</literal> </entry>
- <entry><type>time</type> '01:00' + <type>interval</type> '3 hours'</entry>
- <entry><type>time</type> '04:00'</entry>
+ <entry><literal>time '01:00' + interval '3 hours'</literal></entry>
+ <entry><literal>time '04:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
- <entry><type>timestamp</type> '2001-09-28 23:00' - <type>interval</type> '23 hours'</entry>
- <entry><type>timestamp</type> '2001-09-28'</entry>
+ <entry><literal>timestamp '2001-09-28 23:00' - interval '23 hours'</literal></entry>
+ <entry><literal>timestamp '2001-09-28'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
- <entry><type>date</type> '2001-09-28' - <type>interval</type> '1 hour'</entry>
- <entry><type>timestamp</type> '2001-09-27 23:00'</entry>
+ <entry><literal>date '2001-09-28' - interval '1 hour'</literal></entry>
+ <entry><literal>timestamp '2001-09-27 23:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
- <entry><type>time</type> '05:00' - <type>interval</type> '2 hours'</entry>
- <entry><type>time</type> '03:00'</entry>
+ <entry><literal>time '05:00' - interval '2 hours'</literal></entry>
+ <entry><literal>time '03:00'</literal></entry>
</row>
<row>
<entry> <literal>-</literal> </entry>
- <entry><type>interval</type> '2 hours' - <type>time</type> '05:00'</entry>
- <entry><type>time</type> '03:00:00'</entry>
+ <entry><literal>interval '2 hours' - time '05:00'</literal></entry>
+ <entry><literal>time '03:00:00'</literal></entry>
</row>
<row>
<entry> <literal>*</literal> </entry>
- <entry><type>interval</type> '1 hour' * <type>int</type> '3'</entry>
- <entry><type>interval</type> '03:00'</entry>
+ <entry><literal>interval '1 hour' * int '3'</literal></entry>
+ <entry><literal>interval '03:00'</literal></entry>
</row>
<row>
<entry> <literal>/</literal> </entry>
- <entry><type>interval</type> '1 hour' / <type>int</type> '3'</entry>
- <entry><type>interval</type> '00:20'</entry>
+ <entry><literal>interval '1 hour' / int '3'</literal></entry>
+ <entry><literal>interval '00:20'</literal></entry>
</row>
</tbody>
</tgroup>
</table>
- </para>
-
- <para>
- The date/time functions are summarized below, with additional
- details in subsequent sections.
<table id="functions-datetime-table">
<title>Date/Time Functions</title>
<row>
<entry><function>current_date</function></entry>
<entry><type>date</type></entry>
- <entry>Today's date; see <link linkend="functions-datetime-current">below</link>
+ <entry>Today's date; see <xref linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<row>
<entry><function>current_time</function></entry>
<entry><type>time with time zone</type></entry>
- <entry>Time of day; see <link linkend="functions-datetime-current">below</link>
+ <entry>Time of day; see <xref linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<row>
<entry><function>current_timestamp</function></entry>
<entry><type>timestamp with time zone</type></entry>
- <entry>Date and time; see <link linkend="functions-datetime-current">below</link>
+ <entry>Date and time; see <xref linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<row>
<entry><function>date_trunc</function>(<type>text</type>, <type>timestamp</type>)</entry>
<entry><type>timestamp</type></entry>
- <entry>Truncate to specified precision; see also <link
- linkend="functions-datetime-trunc">below</link>
+ <entry>Truncate to specified precision; see also <xref
+ linkend="functions-datetime-trunc">
</entry>
<entry><literal>date_trunc('hour', timestamp '2001-02-16 20:38:40')</literal></entry>
<entry><literal>2001-02-16 20:00:00+00</literal></entry>
<entry><function>extract</function>(<parameter>field</parameter> from
<type>timestamp</type>)</entry>
<entry><type>double precision</type></entry>
- <entry>Get subfield; see also <link
- linkend="functions-datetime-extract">below</link>
+ <entry>Get subfield; see also <xref
+ linkend="functions-datetime-extract">
</entry>
<entry><literal>extract(hour from timestamp '2001-02-16 20:38:40')</literal></entry>
<entry><literal>20</literal></entry>
<entry><function>extract</function>(<parameter>field</parameter> from
<type>interval</type>)</entry>
<entry><type>double precision</type></entry>
- <entry>Get subfield; see also <link
- linkend="functions-datetime-extract">below</link>
+ <entry>Get subfield; see also <xref
+ linkend="functions-datetime-extract">
</entry>
<entry><literal>extract(month from interval '2 years 3 months')</literal></entry>
<entry><literal>3</literal></entry>
<row>
<entry><function>localtime</function></entry>
<entry><type>time</type></entry>
- <entry>Time of day; see <link linkend="functions-datetime-current">below</link>
+ <entry>Time of day; see <xref linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<row>
<entry><function>localtimestamp</function></entry>
<entry><type>timestamp</type></entry>
- <entry>Date and time; see <link linkend="functions-datetime-current">below</link>
+ <entry>Date and time; see <xref linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<entry><function>now</function>()</entry>
<entry><type>timestamp</type></entry>
<entry>Current date and time (equivalent to
- <function>current_timestamp</function>); see <link
- linkend="functions-datetime-current">below</link>
+ <function>current_timestamp</function>); see <xref
+ linkend="functions-datetime-current">
</entry>
<entry></entry>
<entry></entry>
<row>
<entry><function>timeofday()</function></entry>
<entry><type>text</type></entry>
- <entry>Current date and time; see <link
- linkend="functions-datetime-current">below</link>
+ <entry>Current date and time; see <xref
+ linkend="functions-datetime-current">
</entry>
<entry><literal>timeofday()</literal></entry>
<entry><literal>Wed Feb 21 17:01:13.000126 2001 EST</literal></entry>
</tbody>
</tgroup>
</table>
- </para>
<sect2 id="functions-datetime-extract">
<title><function>EXTRACT</function>, <function>date_part</function></title>
</synopsis>
<para>
- The <function>extract</function> function retrieves sub-fields
+ The <function>extract</function> function retrieves subfields
from date/time values, such as year or hour.
<replaceable>source</replaceable> is a value expression that
evaluates to type <type>timestamp</type> or <type>interval</type>.
The year field divided by 100
</para>
- <informalexample>
<screen>
SELECT EXTRACT(CENTURY FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
</screen>
- </informalexample>
<para>
Note that the result for the century field is simply the year field
The day (of the month) field (1 - 31)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(DAY FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>16</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
The year field divided by 10
</para>
- <informalexample>
<screen>
SELECT EXTRACT(DECADE FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>200</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
<type>timestamp</type> values only)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(DOW FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>5</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
<para>
The day of the year (1 - 365/366) (for <type>timestamp</type> values only)
</para>
- <informalexample>
+
<screen>
SELECT EXTRACT(DOY FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>47</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
of seconds in the interval
</para>
- <informalexample>
<screen>
SELECT EXTRACT(EPOCH FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>982352320</computeroutput>
SELECT EXTRACT(EPOCH FROM INTERVAL '5 days 3 hours');
<lineannotation>Result: </lineannotation><computeroutput>442800</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
The hour field (0 - 23)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>20</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
000 000. Note that this includes full seconds.
</para>
- <informalexample>
<screen>
SELECT EXTRACT(MICROSECONDS FROM TIME '17:12:28.5');
<lineannotation>Result: </lineannotation><computeroutput>28500000</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
The year field divided by 1000
</para>
- <informalexample>
<screen>
SELECT EXTRACT(MILLENNIUM FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput>
</screen>
- </informalexample>
<para>
Note that the result for the millennium field is simply the year field
1000. Note that this includes full seconds.
</para>
- <informalexample>
<screen>
SELECT EXTRACT(MILLISECONDS FROM TIME '17:12:28.5');
<lineannotation>Result: </lineannotation><computeroutput>28500</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
The minutes field (0 - 59)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(MINUTE FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>38</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
the number of months, modulo 12 (0 - 11)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(MONTH FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2</computeroutput>
SELECT EXTRACT(MONTH FROM INTERVAL '2 years 13 months');
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
<type>timestamp</type> values only)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(QUARTER FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>1</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
implemented by the operating system</simpara></footnote>)
</para>
- <informalexample>
<screen>
SELECT EXTRACT(SECOND FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>40</computeroutput>
SELECT EXTRACT(SECOND FROM TIME '17:12:28.5');
<lineannotation>Result: </lineannotation><computeroutput>28.5</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
<!--
a year is in week 1 of that year.
</para>
- <informalexample>
<screen>
SELECT EXTRACT(WEEK FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>7</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
The year field
</para>
- <informalexample>
<screen>
SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001</computeroutput>
</screen>
- </informalexample>
</listitem>
</varlistentry>
<function>extract</function>.
</para>
- <informalexample>
<screen>
SELECT date_part('day', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>16</computeroutput>
SELECT date_part('hour', INTERVAL '4 hours 3 minutes');
<lineannotation>Result: </lineannotation><computeroutput>4</computeroutput>
</screen>
- </informalexample>
</sect2>
</simplelist>
</para>
- <informalexample>
- <para>
+ <para>
+ Examples:
<screen>
SELECT date_trunc('hour', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-02-16 20:00:00+00</computeroutput>
SELECT date_trunc('year', TIMESTAMP '2001-02-16 20:38:40');
<lineannotation>Result: </lineannotation><computeroutput>2001-01-01 00:00:00+00</computeroutput>
</screen>
- </para>
- </informalexample>
+ </para>
</sect2>
<sect2 id="functions-datetime-current">
<para>
The following functions are available to obtain the current date and/or
time:
- <synopsis>
+<synopsis>
CURRENT_DATE
CURRENT_TIME
CURRENT_TIMESTAMP
LOCALTIMESTAMP
LOCALTIME ( <replaceable>precision</replaceable> )
LOCALTIMESTAMP ( <replaceable>precision</replaceable> )
- </synopsis>
+</synopsis>
<function>CURRENT_TIME</function>,
<function>CURRENT_TIMESTAMP</function>,
<function>LOCALTIME</function>, and
</para>
</note>
- <informalexample>
- <screen>
+ <para>
+ Some examples:
+<screen>
SELECT CURRENT_TIME;
<computeroutput>14:39:53.662522-05</computeroutput>
SELECT LOCALTIMESTAMP;
<computeroutput>2001-12-23 14:39:53.662522</computeroutput>
</screen>
- </informalexample>
+ </para>
<para>
The function <function>now()</function> is the traditional
<para>
There is also <function>timeofday()</function>, which for historical
reasons returns a text string rather than a <type>timestamp</type> value:
- </para>
-
- <informalexample>
<screen>
SELECT timeofday();
Sat Feb 17 19:07:32.000126 2001 EST
</screen>
- </informalexample>
+ </para>
<para>
It is important to realize that
SELECT now();
SELECT TIMESTAMP 'now';
</programlisting>
+ </para>
+
<note>
<para>
- You do not want to use the third form when specifying a DEFAULT
- value while creating a table. The system will convert <literal>now</literal>
+ You do not want to use the third form when specifying a <literal>DEFAULT</>
+ clause while creating a table. The system will convert <literal>now</literal>
to a <type>timestamp</type> as soon as the constant is parsed, so that when
the default value is needed,
the time of the table creation would be used! The first two
behavior of defaulting to the time of row insertion.
</para>
</note>
- </para>
</sect2>
</sect1>
<sect1 id="functions-geometry">
- <title>Geometric Functions and Operators</title>
+ <title>Geometric Functions and Operators</title>
<para>
The geometric types <type>point</type>, <type>box</type>,
<type>lseg</type>, <type>line</type>, <type>path</type>,
<type>polygon</type>, and <type>circle</type> have a large set of
- native support functions and operators.
+ native support functions and operators, shown in <xref
+ linkend="functions-geometry-op-table">, <xref
+ linkend="functions-geometry-func-table">, and <xref
+ linkend="functions-geometry-conv-table">.
</para>
- <table>
+ <table id="functions-geometry-op-table">
<title>Geometric Operators</title>
<tgroup cols="3">
<thead>
</tgroup>
</table>
- <table>
+
+ <table id="functions-geometry-func-table">
<title>Geometric Functions</title>
<tgroup cols="4">
<thead>
</table>
- <table>
+ <table id="functions-geometry-conv-table">
<title>Geometric Type Conversion Functions</title>
<tgroup cols="4">
<thead>
<para>
It is possible to access the two component numbers of a <type>point</>
- as though it were an array with subscripts 0,1. For example, if
+ as though it were an array with subscripts 0, 1. For example, if
<literal>t.p</> is a <type>point</> column then
<literal>SELECT p[0] FROM t</> retrieves the X coordinate;
<literal>UPDATE t SET p[1] = ...</> changes the Y coordinate.
</sect1>
- <sect1 id="functions-net">
- <title>Network Address Type Functions</title>
+ <sect1 id="functions-net">
+ <title>Network Address Type Functions</title>
+ <para>
+ <xref linkend="cidr-inet-operators-table"> shows the operators
+ available for the <type>inet</type> and <type>cidr</type> types.
+ The operators <literal><<</literal>,
+ <literal><<=</literal>, <literal>>></literal>,
+ <literal>>>=</literal> test for subnet inclusion: they
+ consider only the network parts of the two addresses, ignoring any
+ host part, and determine whether one network part is identical to
+ or a subnet of the other.
+ </para>
<table tocentry="1" id="cidr-inet-operators-table">
<title><type>cidr</type> and <type>inet</type> Operators</title>
</tgroup>
</table>
- All of the operators for <type>inet</type> can be applied to
- <type>cidr</type> values as well. The operators
- <literal><<</literal>, <literal><<=</literal>,
- <literal>>></literal>, <literal>>>=</literal>
- test for subnet inclusion: they consider only the network parts
- of the two addresses, ignoring any host part, and determine whether
- one network part is identical to or a subnet of the other.
- </para>
-
+ <para>
+ <xref linkend="cidr-inet-functions-table"> shows the functions
+ available for use with the <type>inet</type> and <type>cidr</type>
+ types. The <function>host()</function>,
+ <function>text()</function>, and <function>abbrev()</function>
+ functions are primarily intended to offer alternative display
+ formats. You can cast a text field to inet using normal casting
+ syntax: <literal>inet(expression)</literal> or
+ <literal>colname::inet</literal>.
+ </para>
- <table tocentry="1" id="cidr-inet-functions">
+ <table tocentry="1" id="cidr-inet-functions-table">
<title><type>cidr</type> and <type>inet</type> Functions</title>
<tgroup cols="5">
<thead>
</tgroup>
</table>
- <para>
- All of the functions for <type>inet</type> can be applied to
- <type>cidr</type> values as well. The <function>host</function>(),
- <function>text</function>(), and <function>abbrev</function>() functions are primarily
- intended to offer alternative display formats. You can cast a text
- field to inet using normal casting syntax: <literal>inet(expression)</literal> or
- <literal>colname::inet</literal>.
- </para>
+ <para>
+ <xref linkend="macaddr-functions-table"> shows the functions
+ available for use with the <type>mac</type> type. The function
+ <function>trunc</function>(<type>macaddr</type>) returns a MAC
+ address with the last 3 bytes set to 0. This can be used to
+ associate the remaining prefix with a manufacturer. The directory
+ <filename>contrib/mac</filename> in the source distribution
+ contains some utilities to create and maintain such an association
+ table.
+ </para>
- <table tocentry="1" id="macaddr-functions">
+ <table tocentry="1" id="macaddr-functions-table">
<title><type>macaddr</type> Functions</title>
<tgroup cols="5">
<thead>
</tgroup>
</table>
- <para>
- The function <function>trunc</function>(<type>macaddr</type>) returns a MAC
- address with the last 3 bytes set to 0. This can be used to
- associate the remaining prefix with a manufacturer. The directory
- <filename>contrib/mac</filename> in the source distribution contains some
- utilities to create and maintain such an association table.
- </para>
-
<para>
The <type>macaddr</type> type also supports the standard relational
operators (<literal>></literal>, <literal><=</literal>, etc.) for
<primary>setval</primary>
</indexterm>
- <table>
+ <para>
+ This section describes <productname>PostgreSQL</productname>'s functions
+ for operating on <firstterm>sequence objects</firstterm>.
+ Sequence objects (also called sequence generators or
+ just sequences) are special single-row tables created with
+ <command>CREATE SEQUENCE</command>. A sequence object is usually used to
+ generate unique identifiers for rows of a table. The sequence functions,
+ listed in <xref linkend="functions-sequence-table">,
+ provide simple, multiuser-safe methods for obtaining successive
+ sequence values from sequence objects.
+ </para>
+
+ <table id="functions-sequence-table">
<title>Sequence Functions</title>
<tgroup cols="3">
<thead>
</tgroup>
</table>
- <para>
- This section describes <productname>PostgreSQL</productname>'s functions
- for operating on <firstterm>sequence objects</firstterm>.
- Sequence objects (also called sequence generators or
- just sequences) are special single-row tables created with
- <command>CREATE SEQUENCE</command>. A sequence object is usually used to
- generate unique identifiers for rows of a table. The sequence functions
- provide simple, multiuser-safe methods for obtaining successive
- sequence values from sequence objects.
- </para>
-
<para>
For largely historical reasons, the sequence to be operated on by
a sequence-function call is specified by a text-string argument.
names, the sequence functions convert their argument to lower case
unless the string is double-quoted. Thus
<programlisting>
-nextval('foo') <lineannotation>operates on sequence </><literal>foo</literal>
-nextval('FOO') <lineannotation>operates on sequence </><literal>foo</literal>
-nextval('"Foo"') <lineannotation>operates on sequence </><literal>Foo</literal>
+nextval('foo') <lineannotation>operates on sequence <literal>foo</literal></>
+nextval('FOO') <lineannotation>operates on sequence <literal>foo</literal></>
+nextval('"Foo"') <lineannotation>operates on sequence <literal>Foo</literal></>
</programlisting>
The sequence name can be schema-qualified if necessary:
<programlisting>
-nextval('myschema.foo') <lineannotation>operates on </><literal>myschema.foo</literal>
-nextval('"myschema".foo') <lineannotation>same as above</lineannotation>
-nextval('foo') <lineannotation>searches search path for
- </><literal>foo</literal>
+nextval('myschema.foo') <lineannotation>operates on <literal>myschema.foo</literal></>
+nextval('"myschema".foo') <lineannotation>same as above</lineannotation>
+nextval('foo') <lineannotation>searches search path for <literal>foo</literal></>
</programlisting>
Of course, the text argument can be the result of an expression,
not only a simple literal, which is occasionally useful.
<listitem>
<para>
Advance the sequence object to its next value and return that
- value. This is done atomically: even if multiple server processes
+ value. This is done atomically: even if multiple sessions
execute <function>nextval</function> concurrently, each will safely receive
a distinct sequence value.
</para>
<listitem>
<para>
Return the value most recently obtained by <function>nextval</function>
- for this sequence in the current server process. (An error is
+ for this sequence in the current session. (An error is
reported if <function>nextval</function> has never been called for this
- sequence in this process.) Notice that because this is returning
- a process-local value, it gives a predictable answer even if other
- server processes are executing <function>nextval</function> meanwhile.
+ sequence in this session.) Notice that because this is returning
+ a session-local value, it gives a predictable answer even if other
+ sessions are executing <function>nextval</function> meanwhile.
</para>
</listitem>
</varlistentry>
the next <function>nextval</function> will return exactly the specified
value, and sequence advancement commences with the following
<function>nextval</function>. For example,
- </para>
- <informalexample>
<screen>
-SELECT setval('foo', 42); <lineannotation>Next nextval() will return 43</lineannotation>
+SELECT setval('foo', 42); <lineannotation>Next <function>nextval()</> will return 43</lineannotation>
SELECT setval('foo', 42, true); <lineannotation>Same as above</lineannotation>
-SELECT setval('foo', 42, false); <lineannotation>Next nextval() will return 42</lineannotation>
+SELECT setval('foo', 42, false); <lineannotation>Next <function>nextval()</> will return 42</lineannotation>
</screen>
- </informalexample>
- <para>
The result returned by <function>setval</function> is just the value of its
second argument.
</para>
</para>
</tip>
- <bridgehead renderas="sect2"><literal>CASE</></bridgehead>
+ <sect2>
+ <title>CASE</title>
<synopsis>
CASE WHEN <replaceable>condition</replaceable> THEN <replaceable>result</replaceable>
omitted and no condition matches, the result is null.
</para>
- <informalexample>
<para>
An example:
<screen>
</computeroutput>
</screen>
</para>
- </informalexample>
<para>
The data types of all the <replaceable>result</replaceable>
to the <function>switch</function> statement in C.
</para>
- <informalexample>
<para>
The example above can be written using the simple
<token>CASE</token> syntax:
</computeroutput>
</screen>
</para>
- </informalexample>
+ </sect2>
- <bridgehead renderas="sect2"><literal>COALESCE</></bridgehead>
+ <sect2>
+ <title>COALESCE</title>
<synopsis>
-<function>COALESCE</function>(<replaceable>value</replaceable>
-<optional>, ...</optional>)
+<function>COALESCE</function>(<replaceable>value</replaceable> <optional>, ...</optional>)
</synopsis>
<para>
SELECT COALESCE(description, short_description, '(none)') ...
</programlisting>
</para>
+ </sect2>
- <bridgehead renderas="sect2"><literal>NULLIF</></bridgehead>
+ <sect2>
+ <title>NULLIF</title>
<indexterm>
<primary>nullif</primary>
</indexterm>
<synopsis>
-<function>NULLIF</function>(<replaceable>value1</replaceable>,
- <replaceable>value2</replaceable>)
+<function>NULLIF</function>(<replaceable>value1</replaceable>, <replaceable>value2</replaceable>)
</synopsis>
<para>
refers to <token>CASE</token>.
</para>
</tip>
+ </sect2>
</sect1>
- <sect1 id="functions-misc">
- <title>Miscellaneous Functions</title>
+ <sect1 id="functions-misc">
+ <title>Miscellaneous Functions</title>
- <table>
+ <para>
+ <xref linkend="functions-misc-session-table"> shows several
+ functions that extract session and system information.
+ </para>
+
+ <table id="functions-misc-session-table">
<title>Session Information Functions</title>
<tgroup cols="3">
<thead>
</thead>
<tbody>
+ <row>
+ <entry><function>current_database()</function></entry>
+ <entry><type>name</type></entry>
+ <entry>name of current database</entry>
+ </row>
+
+ <row>
+ <entry><function>current_schema()</function></entry>
+ <entry><type>name</type></entry>
+ <entry>name of current schema</entry>
+ </row>
+
+ <row>
+ <entry><function>current_schemas(boolean)</function></entry>
+ <entry><type>name[]</type></entry>
+ <entry>names of schemas in search path optionally including implicit schemas</entry>
+ </row>
+
<row>
<entry><function>current_user</function></entry>
<entry><type>name</type></entry>
<entry>user name of current execution context</entry>
</row>
+
<row>
<entry><function>session_user</function></entry>
<entry><type>name</type></entry>
<entry>session user name</entry>
</row>
+
<row>
<entry><function>user</function></entry>
<entry><type>name</type></entry>
<entry>equivalent to <function>current_user</function></entry>
</row>
+
<row>
- <entry><function>current_schema()</function></entry>
- <entry><type>name</type></entry>
- <entry>name of current schema</entry>
- </row>
- <row>
- <entry><function>current_schemas(boolean)</function></entry>
- <entry><type>name[]</type></entry>
- <entry>names of schemas in search path optionally including implicit schemas</entry>
- </row>
- <row>
- <entry><function>current_database()</function></entry>
- <entry><type>name</type></entry>
- <entry>name of current database</entry>
+ <entry><function>version</function></entry>
+ <entry><type>text</type></entry>
+ <entry>PostgreSQL version information</entry>
</row>
</tbody>
</tgroup>
</para>
</note>
- <note>
- <title>Deprecated</title>
- <para>
- The function <function>getpgusername()</function> is an obsolete equivalent
- of <function>current_user</function>.
- </para>
- </note>
-
<para>
<function>current_schema</function> returns the name of the schema that is
at the front of the search path (or a null value if the search path is
</command>
</para>
- <table>
- <title>System Information Functions</title>
- <tgroup cols="3">
- <thead>
- <row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row>
- </thead>
-
- <tbody>
- <row>
- <entry><function>version</function></entry>
- <entry><type>text</type></entry>
- <entry>PostgreSQL version information</entry>
- </row>
- </tbody>
- </tgroup>
- </table>
-
<indexterm zone="functions-misc">
<primary>version</primary>
</indexterm>
server's version.
</para>
- <table>
+ <para>
+ <xref linkend="functions-misc-set-table"> shows the functions
+ available to query and alter run-time configuration parameters.
+ </para>
+
+ <table id="functions-misc-set-table">
<title>Configuration Settings Information Functions</title>
<tgroup cols="3">
<thead>
</programlisting>
</para>
- <table>
+ <para>
+ <xref linkend="functions-misc-access-table"> lists functions that
+ allow the user to query object access privileges programmatically.
+ See <xref linkend="ddl-priv"> for more information about
+ privileges.
+ </para>
+
+ <table id="functions-misc-access-table">
<title>Access Privilege Inquiry Functions</title>
<tgroup cols="3">
<thead>
<literal>USAGE</literal>.
</para>
- <table>
+ <para>
+ <xref linkend="functions-misc-schema-table"> shows functions that
+ determine whether a certain object is <firstterm>visible</> in the
+ current schema search path. A table is said to be visible if its
+ containing schema is in the search path and no table of the same
+ name appears earlier in the search path. This is equivalent to the
+ statement that the table can be referenced by name without explicit
+ schema qualification. For example, to list the names of all
+ visible tables:
+<programlisting>
+SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
+</programlisting>
+ </para>
+
+ <table id="functions-misc-schema-table">
<title>Schema Visibility Inquiry Functions</title>
<tgroup cols="3">
<thead>
</indexterm>
<para>
- <function>pg_table_is_visible</function> checks whether a table
- (or view, or any other kind of <structname>pg_class</> entry) is
- <firstterm>visible</> in the current schema search path. A table
- is said to be visible if its containing schema is in the search path
- and no table of the same name appears earlier in the search path.
- This is equivalent to the statement that the table can be referenced
- by name without explicit schema qualification.
- For example, to list the names of all visible tables:
-<programlisting>
-SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
-</programlisting>
- </para>
-
- <para>
- <function>pg_type_is_visible</function>,
- <function>pg_function_is_visible</function>,
- <function>pg_operator_is_visible</function>, and
- <function>pg_opclass_is_visible</function> perform the same sort of
- visibility check for types, functions, operators, and operator classes,
- respectively. For functions and operators, an object in the search path
- is visible if there is no object of the same name <emphasis>and argument
- data type(s)</> earlier in the path. For operator classes,
- both name and associated index access method are considered.
+ <function>pg_table_is_visible</function> performs the check for
+ tables (or views, or any other kind of <literal>pg_class</> entry).
+ <function>pg_type_is_visible</function>,
+ <function>pg_function_is_visible</function>,
+ <function>pg_operator_is_visible</function>, and
+ <function>pg_opclass_is_visible</function> perform the same sort of
+ visibility check for types, functions, operators, and operator
+ classes, respectively. For functions and operators, an object in
+ the search path is visible if there is no object of the same name
+ <emphasis>and argument data type(s)</> earlier in the path. For
+ operator classes, both name and associated index access method are
+ considered.
</para>
<para>
this way --- if the name can be recognized at all, it must be visible.
</para>
- <table>
+ <indexterm zone="functions-misc">
+ <primary>pg_get_viewdef</primary>
+ </indexterm>
+
+ <indexterm zone="functions-misc">
+ <primary>pg_get_ruledef</primary>
+ </indexterm>
+
+ <indexterm zone="functions-misc">
+ <primary>pg_get_indexdef</primary>
+ </indexterm>
+
+ <indexterm zone="functions-misc">
+ <primary>pg_get_constraintdef</primary>
+ </indexterm>
+
+ <indexterm zone="functions-misc">
+ <primary>pg_get_userbyid</primary>
+ </indexterm>
+
+ <para>
+ <xref linkend="functions-misc-catalog-table"> lists functions that
+ extract information from the system catalogs.
+ <function>pg_get_viewdef()</function>,
+ <function>pg_get_ruledef()</function>,
+ <function>pg_get_indexdef()</function>, and
+ <function>pg_get_constraintdef()</function> respectively
+ reconstruct the creating command for a view, rule, index, or
+ constraint. (Note that this is a decompiled reconstruction, not
+ the verbatim text of the command.) At present
+ <function>pg_get_constraintdef()</function> only works for
+ foreign-key constraints. <function>pg_get_userbyid()</function>
+ extracts a user's name given a <structfield>usesysid</structfield>
+ value.
+ </para>
+
+ <table id="functions-misc-catalog-table">
<title>Catalog Information Functions</title>
<tgroup cols="3">
<thead>
<row>
<entry><function>pg_get_viewdef</function>(<parameter>viewname</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Get CREATE VIEW command for view (<emphasis>deprecated</emphasis>)</entry>
+ <entry>Get <command>CREATE VIEW</> command for view (<emphasis>deprecated</emphasis>)</entry>
</row>
<row>
<entry><function>pg_get_viewdef</function>(<parameter>viewOID</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Get CREATE VIEW command for view</entry>
+ <entry>Get <command>CREATE VIEW</> command for view</entry>
</row>
<row>
<entry><function>pg_get_ruledef</function>(<parameter>ruleOID</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Get CREATE RULE command for rule</entry>
+ <entry>Get <command>CREATE RULE</> command for rule</entry>
</row>
<row>
<entry><function>pg_get_indexdef</function>(<parameter>indexOID</parameter>)</entry>
<entry><type>text</type></entry>
- <entry>Get CREATE INDEX command for index</entry>
+ <entry>Get <command>CREATE INDEX</> command for index</entry>
</row>
<row>
<entry><function>pg_get_constraintdef</function>(<parameter>constraintOID</parameter>)</entry>
<row>
<entry><function>pg_get_userbyid</function>(<parameter>userid</parameter>)</entry>
<entry><type>name</type></entry>
- <entry>Get user name given ID</entry>
+ <entry>Get user name with given ID</entry>
</row>
</tbody>
</tgroup>
</table>
<indexterm zone="functions-misc">
- <primary>pg_get_viewdef</primary>
- </indexterm>
-
- <indexterm zone="functions-misc">
- <primary>pg_get_ruledef</primary>
- </indexterm>
-
- <indexterm zone="functions-misc">
- <primary>pg_get_indexdef</primary>
- </indexterm>
-
- <indexterm zone="functions-misc">
- <primary>pg_get_constraintdef</primary>
+ <primary>obj_description</primary>
</indexterm>
<indexterm zone="functions-misc">
- <primary>pg_get_userbyid</primary>
+ <primary>col_description</primary>
</indexterm>
<para>
- These functions extract information from the system catalogs.
- <function>pg_get_viewdef()</function>,
- <function>pg_get_ruledef()</function>,
- <function>pg_get_indexdef()</function>, and
- <function>pg_get_constraintdef()</function> respectively reconstruct the
- creating command for a view, rule, index, or constraint.
- (Note that this is a decompiled
- reconstruction, not the verbatim text of the command.)
- At present <function>pg_get_constraintdef()</function> only works for
- foreign-key constraints.
- <function>pg_get_userbyid()</function> extracts a user's name given a
- <structfield>usesysid</structfield> value.
+ The function shown in <xref
+ linkend="functions-misc-comment-table"> extract comments
+ previously stored with the <command>COMMENT</command> command. A
+ null value is returned if no comment can be found matching the
+ specified parameters.
</para>
- <table>
+ <table id="functions-misc-comment-table">
<title>Comment Information Functions</title>
<tgroup cols="3">
<thead>
</tgroup>
</table>
- <indexterm zone="functions-misc">
- <primary>obj_description</primary>
- </indexterm>
-
- <indexterm zone="functions-misc">
- <primary>col_description</primary>
- </indexterm>
-
- <para>
- These functions extract comments previously stored with the
- <command>COMMENT</command> command. A null value is returned if
- no comment can be found matching the specified parameters.
- </para>
-
<para>
The two-parameter form of <function>obj_description()</function> returns the
comment for a database object specified by its OID and the name of the
<sect1 id="functions-aggregate">
<title>Aggregate Functions</title>
- <note>
- <title>Author</title>
- <para>
- </para>
- </note>
-
<para>
<firstterm>Aggregate functions</firstterm> compute a single result
- value from a set of input values. The special syntax
- considerations for aggregate functions are explained in <xref
- linkend="syntax-aggregates">. Consult the <citetitle>PostgreSQL
- Tutorial</citetitle> for additional introductory information.
+ value from a set of input values. <xref
+ linkend="functions-aggregate-table"> show the built-in aggregate
+ functions. The special syntax considerations for aggregate
+ functions are explained in <xref linkend="syntax-aggregates">.
+ Consult the &cite-tutorial; for additional introductory
+ information.
</para>
- <table tocentry="1">
+ <table id="functions-aggregate-table">
<title>Aggregate Functions</title>
- <tgroup cols="3">
+ <tgroup cols="5">
<thead>
<row>
<entry>Function</entry>
+ <entry>Argument Type</entry>
+ <entry>Return Type</entry>
<entry>Description</entry>
- <entry>Notes</entry>
</row>
</thead>
<tbody>
<row>
- <entry>avg(<replaceable class="parameter">expression</replaceable>)</entry>
- <entry>the average (arithmetic mean) of all input values</entry>
<entry>
<indexterm>
<primary>average</primary>
<secondary>function</secondary>
</indexterm>
- Finding the average value is available on the following data
- types: <type>smallint</type>, <type>integer</type>,
+ <function>avg(<replaceable class="parameter">expression</replaceable>)</function>
+ </entry>
+ <entry>
+ <type>smallint</type>, <type>integer</type>,
<type>bigint</type>, <type>real</type>, <type>double
- precision</type>, <type>numeric</type>, <type>interval</type>.
- The result is of type <type>numeric</type> for any integer type
- input, <type>double precision</type> for floating-point input,
- otherwise the same as the input data type.
+ precision</type>, <type>numeric</type>, or <type>interval</type>.
+ </entry>
+ <entry>
+ <type>numeric</type> for any integer type argument,
+ <type>double precision</type> for a floating-point argument,
+ otherwise the same as the argument data type
</entry>
+ <entry>the average (arithmetic mean) of all input values</entry>
</row>
<row>
- <entry><function>count</function>(*)</entry>
+ <entry><function>count(*)</function></entry>
+ <entry></entry>
+ <entry><type>bigint</type></entry>
<entry>number of input values</entry>
- <entry>The return value is of type <type>bigint</type>.</entry>
</row>
<row>
- <entry><function>count</function>(<replaceable class="parameter">expression</replaceable>)</entry>
+ <entry><function>count(<replaceable class="parameter">expression</replaceable>)</function></entry>
+ <entry>any</entry>
+ <entry><type>bigint</type></entry>
<entry>
- Counts the input values for which the value of <replaceable
- class="parameter">expression</replaceable> is not null.
+ number of input values for which the value of <replaceable
+ class="parameter">expression</replaceable> is not null
</entry>
- <entry>The return value is of type <type>bigint</type>.</entry>
</row>
<row>
- <entry><function>max</function>(<replaceable class="parameter">expression</replaceable>)</entry>
- <entry>the maximum value of <replaceable class="parameter">expression</replaceable> across all input values</entry>
+ <entry><function>max(<replaceable class="parameter">expression</replaceable>)</function></entry>
+ <entry>any numeric, string, or date/time type</entry>
+ <entry>same as argument type</entry>
<entry>
- Available for all numeric, string, and date/time types. The
- result has the same type as the input expression.
+ maximum value of <replaceable
+ class="parameter">expression</replaceable> across all input
+ values
</entry>
</row>
<row>
- <entry><function>min</function>(<replaceable class="parameter">expression</replaceable>)</entry>
- <entry>the minimum value of <replaceable class="parameter">expression</replaceable> across all input values</entry>
+ <entry><function>min(<replaceable class="parameter">expression</replaceable>)</function></entry>
+ <entry>any numeric, string, or date/time type</entry>
+ <entry>same as argument type</entry>
<entry>
- Available for all numeric, string, and date/time types. The
- result has the same type as the input expression.
+ minimum value of <replaceable
+ class="parameter">expression</replaceable> across all input
+ values
</entry>
</row>
<row>
- <entry><function>stddev</function>(<replaceable
- class="parameter">expression</replaceable>)</entry>
- <entry>the sample standard deviation of the input values</entry>
<entry>
<indexterm>
<primary>standard deviation</primary>
</indexterm>
- Finding the standard deviation is available on the following
- data types: <type>smallint</type>, <type>integer</type>,
+ <function>stddev(<replaceable class="parameter">expression</replaceable>)</function>
+ </entry>
+ <entry>
+ <type>smallint</type>, <type>integer</type>,
<type>bigint</type>, <type>real</type>, <type>double
- precision</type>, <type>numeric</type>. The result is of type
- <type>double precision</type> for floating-point input,
+ precision</type>, or <type>numeric</type>.
+ </entry>
+ <entry>
+ <type>double precision</type> for floating-point arguments,
otherwise <type>numeric</type>.
</entry>
+ <entry>sample standard deviation of the input values</entry>
</row>
<row>
- <entry><function>sum</function>(<replaceable class="parameter">expression</replaceable>)</entry>
- <entry>sum of <replaceable class="parameter">expression</replaceable> across all input values</entry>
+ <entry><function>sum(<replaceable class="parameter">expression</replaceable>)</function></entry>
<entry>
- Summation is available on the following data types:
<type>smallint</type>, <type>integer</type>,
<type>bigint</type>, <type>real</type>, <type>double
- precision</type>, <type>numeric</type>, <type>interval</type>.
- The result is of type <type>bigint</type> for <type>smallint</type>
- or <type>integer</type> input, <type>numeric</type> for
- <type>bigint</type>
- input, <type>double precision</type> for floating-point input,
- otherwise the same as the input data type.
+ precision</type>, <type>numeric</type>, or
+ <type>interval</type>
+ </entry>
+ <entry>
+ <type>bigint</type> for <type>smallint</type> or
+ <type>integer</type> arguments, <type>numeric</type> for
+ <type>bigint</type> arguments, <type>double precision</type>
+ for floating-point arguments, otherwise the same as the
+ argument data type
</entry>
+ <entry>sum of <replaceable class="parameter">expression</replaceable> across all input values</entry>
</row>
<row>
- <entry><function>variance</function>(<replaceable
- class="parameter">expression</replaceable>)</entry>
- <entry>the sample variance of the input values</entry>
<entry>
<indexterm>
<primary>variance</primary>
</indexterm>
- The variance is the square of the standard deviation. The
- supported data types and result types are the same as for
- standard deviation.
+ <function>variance</function>(<replaceable class="parameter">expression</replaceable>)
+ </entry>
+ <entry>
+ <type>smallint</type>, <type>integer</type>,
+ <type>bigint</type>, <type>real</type>, <type>double
+ precision</type>, or <type>numeric</type>.
+ </entry>
+ <entry>
+ <type>double precision</type> for floating-point arguments,
+ otherwise <type>numeric</type>.
</entry>
+ <entry>sample variance of the input values (square of the sample standard deviation)</entry>
</row>
</tbody>
</table>
<para>
- It should be noted that except for <function>COUNT</function>,
+ It should be noted that except for <function>count</function>,
these functions return a null value when no rows are selected. In
- particular, <function>SUM</function> of no rows returns null, not
- zero as one might expect. <function>COALESCE</function> may be
+ particular, <function>sum</function> of no rows returns null, not
+ zero as one might expect. The function <function>coalesce</function> may be
used to substitute zero for null when necessary.
</para>
Boolean (true/false) results.
</para>
- <bridgehead renderas="sect2">EXISTS</bridgehead>
+ <sect2>
+ <title>EXISTS</title>
<synopsis>
EXISTS ( <replaceable>subquery</replaceable> )
</synopsis>
<para>
- The argument of <token>EXISTS</token> is an arbitrary SELECT statement,
+ The argument of <token>EXISTS</token> is an arbitrary <command>SELECT</> statement,
or <firstterm>subquery</firstterm>. The
subquery is evaluated to determine whether it returns any rows.
If it returns at least one row, the result of <token>EXISTS</token> is
- TRUE; if the subquery returns no rows, the result of <token>EXISTS</token>
- is FALSE.
+ <quote>true</>; if the subquery returns no rows, the result of <token>EXISTS</token>
+ is <quote>false</>.
</para>
<para>
<para>
The subquery will generally only be executed far enough to determine
whether at least one row is returned, not all the way to completion.
- It is unwise to write a subquery that has any side-effects (such as
- calling sequence functions); whether the side-effects occur or not
+ It is unwise to write a subquery that has any side effects (such as
+ calling sequence functions); whether the side effects occur or not
may be difficult to predict.
</para>
Since the result depends only on whether any rows are returned,
and not on the contents of those rows, the output list of the
subquery is normally uninteresting. A common coding convention is
- to write all EXISTS tests in the form
+ to write all <literal>EXISTS</> tests in the form
<literal>EXISTS(SELECT 1 WHERE ...)</literal>. There are exceptions to
this rule however, such as subqueries that use <token>INTERSECT</token>.
</para>
<para>
- This simple example is like an inner join on col2, but it produces at
- most one output row for each tab1 row, even if there are multiple matching
- tab2 rows:
+ This simple example is like an inner join on <literal>col2</>, but
+ it produces at most one output row for each <literal>tab1</> row,
+ even if there are multiple matching <literal>tab2</> rows:
<screen>
SELECT col1 FROM tab1
WHERE EXISTS(SELECT 1 FROM tab2 WHERE col2 = tab1.col2);
</screen>
</para>
+ </sect2>
- <bridgehead renderas="sect2">IN (scalar form)</bridgehead>
+ <sect2>
+ <title>IN (scalar form)</title>
<synopsis>
-<replaceable>expression</replaceable> IN
- <replaceable>value</replaceable><optional>, ...</optional>)
+<replaceable>expression</replaceable> IN (<replaceable>value</replaceable><optional>, ...</optional>)
</synopsis>
<para>
The right-hand side of this form of <token>IN</token> is a parenthesized list
- of scalar expressions. The result is TRUE if the left-hand expression's
+ of scalar expressions. The result is <quote>true</> if the left-hand expression's
result is equal to any of the right-hand expressions. This is a shorthand
notation for
...
</synopsis>
- Note that if the left-hand expression yields NULL, or if there are
+ Note that if the left-hand expression yields null, or if there are
no equal right-hand values and at least one right-hand expression yields
- NULL, the result of the <token>IN</token> construct will be NULL, not FALSE.
+ null, the result of the <token>IN</token> construct will be null, not false.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<note>
seems best to document it in the same place as subquery <token>IN</token>.
</para>
</note>
+ </sect2>
- <bridgehead renderas="sect2">IN (subquery form)</bridgehead>
+ <sect2>
+ <title>IN (subquery form)</title>
<synopsis>
<replaceable>expression</replaceable> IN (<replaceable>subquery</replaceable>)
The right-hand side of this form of <token>IN</token> is a parenthesized
subquery, which must return exactly one column. The left-hand expression
is evaluated and compared to each row of the subquery result.
- The result of <token>IN</token> is TRUE if any equal subquery row is found.
- The result is FALSE if no equal row is found (including the special
+ The result of <token>IN</token> is <quote>true</> if any equal subquery row is found.
+ The result is <quote>false</> if no equal row is found (including the special
case where the subquery returns no rows).
</para>
<para>
- Note that if the left-hand expression yields NULL, or if there are
+ Note that if the left-hand expression yields null, or if there are
no equal right-hand values and at least one right-hand row yields
- NULL, the result of the <token>IN</token> construct will be NULL, not FALSE.
+ null, the result of the <token>IN</token> construct will be null, not false.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<para>
</para>
<synopsis>
-(<replaceable>expression</replaceable>,
-<replaceable>expres</replaceable><optional>,</optional>)
- IN (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) IN (<replaceable>subquery</replaceable>)
</synopsis>
<para>
subquery, which must return exactly as many columns as there are
expressions in the left-hand list. The left-hand expressions are
evaluated and compared row-wise to each row of the subquery result.
- The result of <token>IN</token> is TRUE if any equal subquery row is found.
- The result is FALSE if no equal row is found (including the special
+ The result of <token>IN</token> is <quote>true</> if any equal subquery row is found.
+ The result is <quote>false</> if no equal row is found (including the special
case where the subquery returns no rows).
</para>
the normal rules of SQL Boolean expressions. Two rows are considered
equal if all their corresponding members are non-null and equal; the rows
are unequal if any corresponding members are non-null and unequal;
- otherwise the result of that row comparison is unknown (NULL).
- If all the row results are either unequal or NULL, with at least one NULL,
- then the result of <token>IN</token> is NULL.
+ otherwise the result of that row comparison is unknown (null).
+ If all the row results are either unequal or null, with at least one null,
+ then the result of <token>IN</token> is null.
</para>
+ </sect2>
- <bridgehead renderas="sect2">NOT IN (scalar form)</bridgehead>
+ <sect2>
+ <title>NOT IN (scalar form)</title>
<synopsis>
-<replaceable>expression</replaceable> NOT IN
- <replaceable>value</replaceable><optional>, ...</optional>)
+<replaceable>expression</replaceable> NOT IN (<replaceable>value</replaceable><optional>, ...</optional>)
</synopsis>
<para>
The right-hand side of this form of <token>NOT IN</token> is a parenthesized list
- of scalar expressions. The result is TRUE if the left-hand expression's
+ of scalar expressions. The result is <quote>true</quote> if the left-hand expression's
result is unequal to all of the right-hand expressions. This is a shorthand
notation for
...
</synopsis>
- Note that if the left-hand expression yields NULL, or if there are
+ Note that if the left-hand expression yields null, or if there are
no equal right-hand values and at least one right-hand expression yields
- NULL, the result of the <token>NOT IN</token> construct will be NULL, not TRUE
+ null, the result of the <token>NOT IN</token> construct will be null, not true
as one might naively expect.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<tip>
It's best to express your condition positively if possible.
</para>
</tip>
+ </sect2>
- <bridgehead renderas="sect2">NOT IN (subquery form)</bridgehead>
+ <sect2>
+ <title>NOT IN (subquery form)</title>
<synopsis>
<replaceable>expression</replaceable> NOT IN (<replaceable>subquery</replaceable>)
The right-hand side of this form of <token>NOT IN</token> is a parenthesized
subquery, which must return exactly one column. The left-hand expression
is evaluated and compared to each row of the subquery result.
- The result of <token>NOT IN</token> is TRUE if only unequal subquery rows
+ The result of <token>NOT IN</token> is <quote>true</> if only unequal subquery rows
are found (including the special case where the subquery returns no rows).
- The result is FALSE if any equal row is found.
+ The result is <quote>false</> if any equal row is found.
</para>
<para>
- Note that if the left-hand expression yields NULL, or if there are
+ Note that if the left-hand expression yields null, or if there are
no equal right-hand values and at least one right-hand row yields
- NULL, the result of the <token>NOT IN</token> construct will be NULL, not TRUE.
+ null, the result of the <token>NOT IN</token> construct will be null, not true.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<para>
</para>
<synopsis>
-(<replaceable>expression</replaceable>,
-<replaceable>expres</replaceable><optional>,</optional>)
- NOT IN (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) NOT IN (<replaceable>subquery</replaceable>)
</synopsis>
<para>
subquery, which must return exactly as many columns as there are
expressions in the left-hand list. The left-hand expressions are
evaluated and compared row-wise to each row of the subquery result.
- The result of <token>NOT IN</token> is TRUE if only unequal subquery rows
+ The result of <token>NOT IN</token> is <quote>true</> if only unequal subquery rows
are found (including the special case where the subquery returns no rows).
- The result is FALSE if any equal row is found.
+ The result is <quote>false</> if any equal row is found.
</para>
<para>
the normal rules of SQL Boolean expressions. Two rows are considered
equal if all their corresponding members are non-null and equal; the rows
are unequal if any corresponding members are non-null and unequal;
- otherwise the result of that row comparison is unknown (NULL).
- If all the row results are either unequal or NULL, with at least one NULL,
- then the result of <token>NOT IN</token> is NULL.
+ otherwise the result of that row comparison is unknown (null).
+ If all the row results are either unequal or null, with at least one null,
+ then the result of <token>NOT IN</token> is null.
</para>
+ </sect2>
- <bridgehead renderas="sect2">ANY</bridgehead>
+ <sect2>
+ <title>ANY/SOME</title>
<synopsis>
-<replaceable>expression</replaceable>
-<replaceable>oper</replaceable> ANY (<replaceable>subquery</replaceable>)
-<replaceable>expression</replaceable>
-<replaceable>oper</replaceable> SOME (<replaceable>subquery</replaceable>)
+<replaceable>expression</replaceable> <replaceable>operator</replaceable> ANY (<replaceable>subquery</replaceable>)
+<replaceable>expression</replaceable> <replaceable>operator</replaceable> SOME (<replaceable>subquery</replaceable>)
</synopsis>
<para>
is evaluated and compared to each row of the subquery result using the
given <replaceable>operator</replaceable>, which must yield a Boolean
result.
- The result of <token>ANY</token> is TRUE if any true result is obtained.
- The result is FALSE if no true result is found (including the special
+ The result of <token>ANY</token> is <quote>true</> if any true result is obtained.
+ The result is <quote>false</> if no true result is found (including the special
case where the subquery returns no rows).
</para>
<para>
Note that if there are no successes and at least one right-hand row yields
- NULL for the operator's result, the result of the <token>ANY</token> construct
- will be NULL, not FALSE.
+ null for the operator's result, the result of the <token>ANY</token> construct
+ will be null, not false.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<para>
</para>
<synopsis>
-(<replaceable>expression</replaceable>,
-<replaceable>expres</replaceable><optional>,</optional>optiona<replaceable></replaceable> ANY (<replaceable>subquery</replaceable>)
-(<replaceable>expression</replaceable>,
-<replaceable>expres</replaceable><optional>,</optional>optiona<replaceable></replaceable> SOME (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</> ANY (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</> SOME (<replaceable>subquery</replaceable>)
</synopsis>
<para>
using the given <replaceable>operator</replaceable>. Presently,
only <literal>=</literal> and <literal><></literal> operators are allowed
in row-wise <token>ANY</token> queries.
- The result of <token>ANY</token> is TRUE if any equal or unequal row is
+ The result of <token>ANY</token> is <quote>true</> if any equal or unequal row is
found, respectively.
- The result is FALSE if no such row is found (including the special
+ The result is <quote>false</> if no such row is found (including the special
case where the subquery returns no rows).
</para>
the normal rules of SQL Boolean expressions. Two rows are considered
equal if all their corresponding members are non-null and equal; the rows
are unequal if any corresponding members are non-null and unequal;
- otherwise the result of that row comparison is unknown (NULL).
- If there is at least one NULL row result, then the result of <token>ANY</token>
- cannot be FALSE; it will be TRUE or NULL.
+ otherwise the result of that row comparison is unknown (null).
+ If there is at least one null row result, then the result of <token>ANY</token>
+ cannot be false; it will be true or null.
</para>
+ </sect2>
- <bridgehead renderas="sect2">ALL</bridgehead>
+ <sect2>
+ <title>ALL</title>
<synopsis>
-<replaceable>expression</replaceable>
-<replaceable>oper</replaceable> ALL (<replaceable>subquery</replaceable>)
+<replaceable>expression</replaceable> <replaceable>operator</replaceable> ALL (<replaceable>subquery</replaceable>)
</synopsis>
<para>
is evaluated and compared to each row of the subquery result using the
given <replaceable>operator</replaceable>, which must yield a Boolean
result.
- The result of <token>ALL</token> is TRUE if all rows yield TRUE
+ The result of <token>ALL</token> is <quote>true</> if all rows yield true
(including the special case where the subquery returns no rows).
- The result is FALSE if any false result is found.
+ The result is <quote>false</> if any false result is found.
</para>
<para>
<para>
Note that if there are no failures but at least one right-hand row yields
- NULL for the operator's result, the result of the <token>ALL</token> construct
- will be NULL, not TRUE.
+ null for the operator's result, the result of the <token>ALL</token> construct
+ will be null, not true.
This is in accordance with SQL's normal rules for Boolean combinations
- of NULL values.
+ of null values.
</para>
<para>
</para>
<synopsis>
-(<replaceable>expression</replaceable>, <replaceable>expression</replaceable><optional>, ...</optional>) <replaceable>operator</replaceable> ALL (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> ALL (<replaceable>subquery</replaceable>)
</synopsis>
<para>
using the given <replaceable>operator</replaceable>. Presently,
only <literal>=</literal> and <literal><></literal> operators are allowed
in row-wise <token>ALL</token> queries.
- The result of <token>ALL</token> is TRUE if all subquery rows are equal
+ The result of <token>ALL</token> is <quote>true</> if all subquery rows are equal
or unequal, respectively (including the special
case where the subquery returns no rows).
- The result is FALSE if any row is found to be unequal or equal,
+ The result is <quote>false</> if any row is found to be unequal or equal,
respectively.
</para>
the normal rules of SQL Boolean expressions. Two rows are considered
equal if all their corresponding members are non-null and equal; the rows
are unequal if any corresponding members are non-null and unequal;
- otherwise the result of that row comparison is unknown (NULL).
- If there is at least one NULL row result, then the result of <token>ALL</token>
- cannot be TRUE; it will be FALSE or NULL.
+ otherwise the result of that row comparison is unknown (null).
+ If there is at least one null row result, then the result of <token>ALL</token>
+ cannot be true; it will be false or null.
</para>
+ </sect2>
- <bridgehead renderas="sect2">Row-wise comparison</bridgehead>
+ <sect2>
+ <title>Row-wise Comparison</title>
<synopsis>
-(<replaceable>expression</replaceable>, <replaceable>expression</replaceable><optional>, ...</optional>) <replaceable>operator</replaceable> (<replaceable>subquery</replaceable>)
-(<replaceable>expression</replaceable>, <replaceable>expression</replaceable><optional>, ...</optional>) <replaceable>operator</replaceable> (<replaceable>expression</replaceable> <replaceable>expression</replaceable><optional>, ...</optional>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> (<replaceable>subquery</replaceable>)
+(<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>) <replaceable>operator</replaceable> (<replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ...</optional>)
</synopsis>
<para>
parenthesized subquery, which must return exactly as many columns as there
are expressions on the left-hand side. Furthermore, the subquery cannot
return more than one row. (If it returns zero rows, the result is taken to
- be NULL.) The left-hand side is evaluated and compared row-wise to the
+ be null.) The left-hand side is evaluated and compared row-wise to the
single subquery result row, or to the right-hand expression list.
Presently, only <literal>=</literal> and <literal><></literal> operators are allowed
in row-wise comparisons.
- The result is TRUE if the two rows are equal or unequal, respectively.
+ The result is <quote>true</> if the two rows are equal or unequal, respectively.
</para>
<para>
the normal rules of SQL Boolean expressions. Two rows are considered
equal if all their corresponding members are non-null and equal; the rows
are unequal if any corresponding members are non-null and unequal;
- otherwise the result of the row comparison is unknown (NULL).
+ otherwise the result of the row comparison is unknown (null).
</para>
-
+ </sect2>
</sect1>
</chapter>
projects / users / bernd / postgres.git / commitdiff