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Chapter 3. Operators and Functions

PostgreSQL provides a large number of functions and operators for the built-in data types. Users can also define their own functions and operators, as described in the Programmer's Guide. The psql commands \df and \do can be used to show the list of all available functions and operators, respectively.

If you are concerned about portability then take note that most of the functions and operators described in this chapter, with the exception of the most trivial arithmetic and comparison operators and some explicitly marked functions, are not specified by the SQL standard.

Logical Operators

The logical operators available are:

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

aba AND ba OR b
TRUETRUETRUETRUE
TRUEFALSEFALSETRUE
TRUENULLNULLTRUE
FALSEFALSEFALSEFALSE
FALSENULLFALSENULL
NULLNULLNULLNULL

aNOT a
TRUEFALSE
FALSETRUE
NULLNULL