How to Drop All Tables Whose Names Begin With a Certain String

In many SQL databases, especially in large-scale applications where we may find that certain tables follow a naming convention or pattern. In some cases, we might need to drop all tables that start with a particular prefix without having to drop them individually.

In this article, We will learn about dropping all tables whose names begin with a certain string in a stepwise manner in detail and so on.

How to Drop Tables Based on a Name Prefix?

Let's learn step by step how to Drop Tables Based on a Name Prefix are defined below:

• The first step is to query the database's system metadata to get a list of tables whose names start with a specific prefix.
• Once we have the list of table names, we can create a dynamic script that will drop those tables.
• After generating the dynamic query, we can execute it to drop the desired tables.

Example of Drop all tables whose names begin with a certain string in SQL Server

In SQL Server, we can use sys.tables to get a list of all tables in the current database. Here's the SQL code to drop all tables that start with a specific prefix:

DECLARE @prefix NVARCHAR(100) = 'users_';  -- Define the prefix
DECLARE @sql NVARCHAR(MAX) = '';  -- Variable to store the dynamic SQL

-- Generate the dynamic SQL to drop tables
SELECT @sql = @sql + 'DROP TABLE IF EXISTS ' + QUOTENAME(name) + ';'
FROM sys.tables
WHERE name LIKE @prefix + '%';

-- Execute the generated SQL
EXEC sp_executesql @sql;

Explanation:

Let's understand the above query in detail as below:

• Set the Prefix: The @prefix variable is defined with the desired prefix.
• Generate SQL: The QUOTENAME function ensures that the table names are safely included in the SQL query. This prevents SQL injection or issues with special characters in table names.
• Execute SQL: The sp_executesql procedure runs the dynamically generated SQL.

Important Considerations

• Permissions: Always ensure that the user executing the script has sufficient privileges to drop tables. We need DROP privileges to perform this operation.
• Foreign Key Constraints: If the tables we are trying to drop have foreign key constraints, you may encounter errors. To handle this, we might need to disable foreign key checks temporarily (in MySQL, this is done with SET FOREIGN_KEY_CHECKS = 0;).
• Data Loss: Dropping tables will permanently delete all the data contained in those tables. Always ensure we have a backup of our data before performing such operations.
• Database Name: In the case of MySQL or PostgreSQL and make sure we specify the correct database name in the query (in table_schema for MySQL or PostgreSQL).
• Testing: It's always a good idea to test this process on a non-production environment first to ensure it behaves as expected.

Conclusion

Overall, dropping tables based on a prefix is a powerful technique when working with large databases that contain multiple tables following a specific naming convention. By querying system metadata and using dynamic SQL, you can easily drop all tables whose names start with a given string.