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 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
Example 8-2 shows that boolean values are output using the letters t and f.
boolean uses 1 byte of storage.