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PostgreSQL 9.1.24 Documentation
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8.6. 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:

TRUE

't'

'true'

'y'

'yes'

'on'

'1'

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

FALSE

'f'

'false'

'n'

'no'

'off'

'0'

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

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

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