5.6. 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).

Example 5-2. 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 5-2 shows that boolean values are output using the letters t and f.

Tip: Values of the boolean type cannot be cast directly to other types (e.g., CAST (boolval AS integer) does not work). This can be accomplished using the CASE expression: CASE WHEN boolval THEN 'value if true' ELSE 'value if false' END. See also Section 6.12.

boolean uses 1 byte of storage.