The Result typeclass, for converting a single value in a row returned by a SQL query into a more useful Haskell representation.

A Haskell numeric type is considered to be compatible with all MySQL numeric types that are less accurate than it. For instance, the Haskell Double type is compatible with the MySQL Long type because it can represent a Long exactly. On the other hand, since a Double might lose precision if representing a LongLong, the two are not considered compatible.