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
character_data is used for any other
kind of text data.
A domain over the type
timestamp with time
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
Every column in the information schema has one of these five types.
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