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6.6 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:

• TRUE
• 't'
• 'true'
• 'y'
• 'yes'
• '1'

For the “false” state, the following values can be used:

• FALSE
• 'f'
• 'false'
• 'n'
• 'no'
• '0'

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

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

section 6.6 Boolean Type shows that boolean values are output using the letters t and f.

boolean uses 1 byte of storage.