Syntax:IFNULL(expr1,expr2)If expr1 is not NULL, IFNULL() returns expr1; otherwise it returnsexpr2.
mysql> SELECT IFNULL(1,0); -> 1mysql> SELECT IFNULL(NULL,10); -> 10mysql> SELECT IFNULL(1/0,10); -> 10mysql> SELECT IFNULL(1/0,'yes'); -> 'yes'