PostgreSQL supports left unary, right unary, and binary operators. Operators can be overloaded; that is, the same operator name can be used for different operators that have different numbers and types of arguments. If there is an ambiguous situation and the system cannot determine the correct operator to use, it will return an error. You may have to typecast the left and/or right operands to help it understand which operator you meant to use.
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 Chapter 4. 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.
The logical operators available are:
| AND |
| OR |
| NOT |