37.2. Data Types
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:
cardinal_numberA nonnegative integer.
character_dataA character string (without specific maximum length).
sql_identifierA character string. This type is used for SQL identifiers, the type
character_datais used for any other kind of text data.time_stampA domain over the type
timestamp with time zoneyes_or_noA character string domain that contains either
YESorNO. This is used to represent Boolean (true/false) data in the information schema. (The information schema was invented before the typebooleanwas 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.