PostgreSQL™ provides the standard SQL type boolean; see Table 8.19, “Boolean Data Type”. The boolean type can have several states: “true”, “false”, and a third state, “unknown”, which 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.
Example 8.2, “Using the boolean Type” shows that
boolean values are output using the letters
t
and f
.