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Chapter 5. 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