数据库分组查询

学生表student 字段id和name

课程表class 字段id和name

成绩表score 字段sid（学生id）、cid（课程id）、level成绩

查出所有满足有三科以上学科并且分数大于80分的学生名字集合

select s.sid,count(*) from score s where s.`level`>80 GROUP BY s.sid;

select s.sid ,count(*) from score s where s.`level`>80   GROUP BY s.sid HAVING count(*)>2  ;

select  name  from student  where id in  (select s.sid   from score s where s.`level`>80   GROUP BY s.sid HAVING count(*)>2)