**Table of Contents**- 4.1. Logical Operators
- 4.2. Comparison Operators
- 4.3. Mathematical Functions and Operators
- 4.4. String Functions and Operators
- 4.5. Binary String Functions and Operators
- 4.6. Pattern Matching
- 4.6.1. Pattern Matching with
`LIKE` - 4.6.2. POSIX Regular Expressions

- 4.6.1. Pattern Matching with
- 4.7. Data Type Formatting Functions
- 4.8. Date/Time Functions and Operators
- 4.8.1.
`EXTRACT`,`date_part` - 4.8.2.
`date_trunc` - 4.8.3. Current Date/Time

- 4.8.1.
- 4.9. Geometric Functions and Operators
- 4.10. Network Address Type Functions
- 4.11. Sequence-Manipulation Functions
- 4.12. Conditional Expressions
- 4.13. Miscellaneous Functions
- 4.14. Aggregate Functions
- 4.15. Subquery Expressions

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 actually
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. Some of this extended functionality is present in other RDBMS products, and in many cases this functionality is compatible and consistent between various products.

The usual logical operators are available:

AND |

OR |

NOT |