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PostgreSQL provides the
standard SQL type boolean; see Table 8-19.
The boolean type can have one of only two
states: "true" or "false". A third state, "unknown", is represented by the SQL null value.
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