Postgres supports bool as the SQL3 boolean type. bool can have one of only two states: 'true' or 'false'. A third state, 'unknown', is not implemented and is not suggested in SQL3; NULL is an effective substitute. bool can be used in any boolean expression, and boolean expressions always evaluate to a result compatible with this type.
bool uses 4 bytes of storage.
Table 8-12. Postgres Boolean Type
|True||'t'||TRUE, 't', 'true', 'y', 'yes', '1'|
|False||'f'||FALSE, 'f', 'false', 'n', 'no', '0'|
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