# COALESCE

Coalesce returns the first none null argument from a set of arguments. Only the first non null argument is return, all subsequent arguments are ignored. The function will evaluate to null if all arguments are null.

# Single non null argument

PGSQL> SELECT COALESCE(NULL, NULL, 'HELLO WORLD');

coalesce
--------
'HELLO WORLD'

# Multiple non null arguments

PGSQL> SELECT COALESCE(NULL, NULL, 'first non null', null, null, 'second non null');

coalesce
--------
'first non null'

# All null arguments

PGSQL> SELECT COALESCE(NULL, NULL, NULL);

coalesce
--------