8.6. Boolean Type

PostgreSQL provides the standard SQL type boolean . boolean can have one of only two states: "true" or "false" . A third state, "unknown" , is represented by the SQL null value.

Valid literal values for the "true" state are:


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


Using the key words TRUE and FALSE is preferred (and SQL -compliant).

Example 8-2. Using the boolean type

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 est SELECT * FROM test1 WHERE a; a | b ---+--------- t | sic est

Example 8-2 shows that boolean values are output using the letters t and f .

boolean uses 1 byte of storage.