1、查询平均分大于80分的学生的姓名
select name,avg(score) as sc from grade group by name having avg(score)>80;
2、查询出所有科目都大于80分学生的姓名
select name from grade group by name having min(score)>80;
3、SQL求出分数都大于80的学生姓名及其总成绩
select name,sum(score) as su from grade group by name having avg(score)>80;