Postgresql Boolean Data Type Examples

Boolean Type:

• PostgreSQL provides the standard SQL type boolean; 
• The boolean type can have several states: "true", "false", and a third state, "unknown", which is represented by the SQL null value.

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.

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