Documentation → PostgreSQL 8.4

Supported Versions: Current (17) / 16 / 15 / 14 / 13

Development Versions: devel

Unsupported versions: 12 / 11 / 10 / 9.6 / 9.5 / 9.4 / 9.3 / 9.2 / 9.1 / 9.0 / 8.4 / 8.3 / 8.2

This documentation is for an unsupported version of PostgreSQL.
You may want to view the same page for the current version, or one of the other supported versions listed above instead.

PostgreSQL 8.4.22 Documentation
Prev	Fast Backward	Chapter 9. Functions and Operators	Fast Forward	Next

9.1. Logical Operators

The usual logical operators are available:

AND

OR

NOT

SQL uses a three-valued Boolean logic where the null value represents "unknown". Observe the following truth tables:

`a`	`b`	`a` AND `b`	`a` OR `b`
TRUE	TRUE	TRUE	TRUE
TRUE	FALSE	FALSE	TRUE
TRUE	NULL	NULL	TRUE
FALSE	FALSE	FALSE	FALSE
FALSE	NULL	FALSE	NULL
NULL	NULL	NULL	NULL

`a`	NOT `a`
TRUE	FALSE
FALSE	TRUE
NULL	NULL

The operators AND and OR are commutative, that is, you can switch the left and right operand without affecting the result. But see Section 4.2.13 for more information about the order of evaluation of subexpressions.

Prev	Home	Next
Functions and Operators	Up	Comparison Operators