8.6. Boolean Type

PostgreSQL provides the standardSQL typeboolean; seeTable 8-19. Theboolean type can have several states:"true","false", and a third state,"unknown", which is represented by theSQL null value.

Valid literal values for the"true" state are:

For the"false" state, the following values can be used:

Leading or trailing whitespace is ignored, and case does not matter. The key wordsTRUE andFALSE are the preferred (SQL-compliant) usage.

Example 8-2 shows thatboolean values are output using the letterst andf.

CREATE TABLE test1 (a boolean, b text);INSERT INTO test1 VALUES (TRUE, 'sic est');INSERT INTO test1 VALUES (FALSE, 'non est');SELECT * FROM test1; a |    b---+--------- t | sic est f | non estSELECT * FROM test1 WHERE a; a |    b---+--------- t | sic est