Evaluates the arguments in order and returns the current value of the first expression that initially does not evaluate to NULL.
COALESCE ( expression [ ,...n ] )
Is an expression of any type.
Returns the data type of expression with the highest data type precedence. If all expressions are nonnullable, the result is typed as nonnullable.
SELECT COALESCE(NULL, NULL, NULL, 1, 2, 3);