Boolean Type

PostgreSQL provides the standard SQL type boolean ; see Table 8-19 . The boolean type can have several states: "true" , "false" , and a third state, "unknown" , which is represented by the SQL null value.

Table 8-19. Boolean Data Type

Name Storage Size Description
boolean 1 byte state of true or false

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 words TRUE and FALSE are the preferred ( SQL -compliant) usage.

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

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

 a |    b
 t | sic est