nvl(expr1, expr2)
If the value of expr1 is not null, expr1 is returned, otherwise expr2 is returned
mysql> select nvl(1,0); +--------------+ | nvl(1, 0) | +--------------+ | 1 | +--------------+ mysql> select nvl(null,10); +------------------+ | nvl(NULL, 10) | +------------------+ | 10 | +------------------+
NVL