目录
2. 查询平均成绩大于60分的同学的学号和平均成绩并从高到低降序排序；
3. 查询所有同学的学号、姓名、选课数、总成绩，并按总成绩降序排序；
提前准备的表
1. 学生表
2. 教师表
3. 课程表
4. 成绩表
练习开始
1. 查询1号课程比2号课程成绩高的所有学生的学号；
select a.S_id
from
(select score , S_id from Score where C_id = 1) a,
(select score , S_id from Score where C_id = 2) b
where
a.score > b.score and a.S_id = b.S_id;
2. 查询平均成绩大于60分的同学的学号和平均成绩并从高到低降序排序；
select S_id,AVG(score) as AvgScore
from Score
group by S_id
having AvgScore>60
order by AvgScore desc;
3. 查询所有同学的学号、姓名、选课数、总成绩，并按总成绩降序排序；
select s.S_id , s.Sname , count(c.C_id) as courseCount , sum(c.score) as sumScore
from
Student as s left join Score as c
on s.S_id = c.S_id
group by s.Sname
order by sumScore desc;
4. 查询姓"黄"的老师的个数；
select count(T_id) as Count
from Teacher
where Tname like '黄%'
5.查询选修"林老师"课的同学的学号、姓名；
select s.S_id as id,s.Sname as name
from
Student as s,
Course as c,
Score as sc,
(select T_id from Teacher where Tname = '林老师') as t
where
c.T_id = t.T_id and s.S_id = sc.S_id and sc.C_id = c.C_id;
待更新.....
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