1582 - Incorrect parameter count in the call to native function 'ISNULL',

错误代码：

SELECT SNUM,AVG(ISNULL(SCORE,0)) FROM SC
WHERE SNUM IN
(
select SNUM from sc 
where score < 90 
group by SNUM 
having count(*)>2)
GROUP BY SNUM

错误提示：

1582 - Incorrect parameter count in the call to native function 'ISNULL',

错误原因：

mysql识别不了ISNULL，支持IFNULL，

修改后代码：

SELECT SNUM,AVG(IFNULL(SCORE,0)) FROM SC
WHERE SNUM IN
(
select SNUM from sc 
where score < 90 
group by SNUM 
having count(*)>2)
GROUP BY SNUM

 运行无误！