The columns of the information schema views use special data types that are defined in the information schema. These are defined as simple domains over ordinary built-in types. You should not use these types for work outside the information schema, but your applications must be prepared for them if they select from the information schema.
These types are:
A nonnegative integer.
A character string (without specific maximum length).
A character string. This type is used for SQL
identifiers, the type
character_data is used for any other kind of
A domain over the type
A character string domain that contains either
NO. This is used to represent Boolean
(true/false) data in the information schema. (The
information schema was invented before the type
boolean was added to the SQL
standard, so this convention is necessary to keep the
information schema backward compatible.)
Every column in the information schema has one of these five types.
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