Logical Operators

PostgreSQL 9.5.3 Documentation
Prev | Up | Chapter 9. Functions and Operators | Next

# 9.1. Logical Operators

The usual logical operators are available:

`AND`
`OR`
`NOT`

SQL uses a three-valued logic system with true, false, and `null`, which 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 4.2.14 for more information about the order of evaluation of subexpressions.

Prev | Home | Next
Functions and Operators | Up | Comparison Operators