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 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 |