The PostgreSQL 9.0 Reference Manual - Volume 1A - SQL Language Reference by The PostgreSQL Global Development Group Paperback (6"x9"), 454 pages ISBN 9781906966041 RRP £14.95 ($19.95) Sales of this book support the PostgreSQL project! Get a printed copy>>>

PostgreSQL 9.0 Reference Manual Volume 1A Buy the book here! >>> support free software

6.6 Boolean Type

PostgreSQL provides the standard SQL type boolean; see Table 6-19. The boolean type 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'
• '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.

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

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