mysql查询各科目分数大于70的学生

1.思路：先查询出分数达到70的科目，再姓名分组找出出现科目次数的学生

SELECT * FROM (SELECT * FROM USER WHERE grade>70)a GROUP BY NAME HAVING COUNT(NAME)>1

 

2.思路2：关联查询，将所有用户的科目关联成一条信息，再分别查询分数

SELECT DISTINCT a.name FROM USER a LEFT JOIN USER b ON a.name=b.name AND a.class!=b.class WHERE a.grade>70 AND b.grade>70

 

3.其实我觉得这种方式性能上还是差很多，，，再补充吧