Functions

PostgreSQL User's Guide
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Chapter 5. Functions

Table of Contents
SQL Functions
Mathematical Functions
String Functions
Date/Time Functions
Formatting Functions
Geometric Functions
IP V4 Functions

Describes the built-in functions available in Postgres.

Many data types have functions available for conversion to other related types. In addition, there are some type-specific functions. Some functions are also available through operators and may be documented as operators only.

SQL Functions

SQL functions are constructs defined by the SQL92 standard which have function-like syntax but which can not be implemented as simple functions.

Table 5-1. SQL Functions

Function	Returns	Description	Example
COALESCE(`list`)	non-NULL	return first non-NULL value in list	COALESCE(rle, c2 + 5, 0)
NULLIF(`input`,`value`)	`input` or NULL	return NULL if `input` = `value`, else `input`	NULLIF(c1, 'N/A')
CASE WHEN `expr` THEN `expr` [...] ELSE `expr` END	`expr`	return expression for first true WHEN clause	CASE WHEN c1 = 1 THEN 'match' ELSE 'no match' END

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IP V4 INET Operators		Mathematical Functions