技術標籤：MySql

目錄

提前準備的表

1. 學生表

2. 教師表

3. 課程表

4. 成績表

練習開始

1. 查詢1號課程比2號課程成績高的所有學生的學號；

2.查詢平均成績大於60分的同學的學號和平均成績並從高到低降序排序；

3.查詢所有同學的學號、姓名、選課數、總成績，並按總成績降序排序；

4.查詢姓"黃"的老師的個數；

5.查詢選修"林老師"課的同學的學號、姓名；

提前準備的表

1. 學生表

2. 教師表

3. 課程表

4. 成績表

練習開始

1. 查詢1號課程比2號課程成績高的所有學生的學號；

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.查詢平均成績大於60分的同學的學號和平均成績並從高到低降序排序；

 select S_id,AVG(score) as AvgScore 
 from Score
 group by S_id
 having AvgScore>60
 order by AvgScore desc;

3.查詢所有同學的學號、姓名、選課數、總成績，並按總成績降序排序；

 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.查詢姓"黃"的老師的個數；

 select count(T_id) as Count
 from Teacher
 where Tname like '黃%'

5.查詢選修"林老師"課的同學的學號、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 = '林老師') 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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