COALESCE
Given a list of values, returns the first non-NULL value.
Syntax
COALESCE ( val, [val, [val ...]])
Arguments
val: any object
Return Type
Returns any object type, according to the type of the first non-NULL value in the list. Returns NULL if all values are NULL.
Examples
SELECT COALESCE(NULL, NULL, 1, 2, 3); +-------------------------------+ | COALESCE(NULL, NULL, 1, 2, 3) | +-------------------------------+ | 1 | +-------------------------------+