Mysql多表练习题30道


SELECT
	s.id sid,
	s.`name` sname,
	c.`name` cname,
	sc.score 
FROM
	student s
	LEFT JOIN scores sc ON s.id = sc.s_id
	LEFT JOIN course c ON c.id = sc.c_id 
WHERE
	s.id = 1;

2.查询各个学科的平均成绩和最高成绩：


SELECT
	c.id,
	c.`name`,
	AVG( sc.score ),
	max( sc.score ) 
FROM
	course c
	LEFT JOIN scores sc ON c.id = sc.c_id 
GROUP BY
	c.id,
	c.`name`;

3.查询所有姓张的同学的各科成绩：


SELECT
	s.id,
	s.`name`,
	c.`name` cname,
	sc.score 
FROM
	student s
	LEFT JOIN scores sc ON sc.s_id = s.id
	LEFT JOIN course c ON c.id = sc.c_id 
WHERE
	s.`name` LIKE '张%';

4.查询每个同学的最高成绩和科目名称


SELECT
	t.id,
	t.NAME,
	c.id,
	c.NAME,
	r.score 
FROM
	(
	SELECT
		s.id,
		s.NAME,(
		SELECT
			max( score ) 
		FROM
			scores r 
		WHERE
			r.s_id = s.id 
		) score 
	FROM
		student s 
	) t
	LEFT JOIN scores r ON r.s_id = t.id 
	AND r.score = t.score
	LEFT JOIN course c ON r.c_id = c.id;

5.查询每个课程的最高分的学生信息


SELECT
	* 
FROM
	student s 
WHERE
	id IN (
	SELECT DISTINCT
		r.s_id 
	FROM
		(
		SELECT
			c.id,
			c.NAME,
			max( score ) score 
		FROM
			student s
			LEFT JOIN scores r ON r.s_id = s.id
			LEFT JOIN course c ON c.id = r.c_id 
		GROUP BY
			c.id,
			c.NAME 
		) t
		LEFT JOIN scores r ON r.c_id = t.id 
	AND t.score = r.score 
	);

6.查询名字中含有'张'或'李'字的学生的信息和各科成绩。


SELECT
	s.id,
	s.NAME sname,
	sc.score,
	c.NAME 
FROM
	student s
	LEFT JOIN scores sc ON s.id = sc.s_id
	LEFT JOIN course c ON sc.c_id = c.id 
WHERE
	s.NAME LIKE '%张%' 
	OR s.NAME LIKE '%李%';

7.查询平均成绩大于70的同学的信息。（子查询）


SELECT
	* 
FROM
	student 
WHERE
	id IN (
	SELECT
		sc.s_id 
	FROM
		scores sc 
	GROUP BY
		sc.s_id 
	HAVING
	avg( sc.score ) >= 70 
	);

8.将学生按照总分数进行排名。（从高到低）


SELECT
	s.id,
	s.NAME,
	sum( sc.score ) score 
FROM
	student s
	LEFT JOIN scores sc ON s.id = sc.s_id 
GROUP BY
	s.id,
	s.NAME 
ORDER BY
	score DESC,
	s.id ASC;

9.查询数学成绩的最高分、最低分、平均分。


SELECT
	c.NAME,
	max( sc.score ),
	min( sc.score ),
	avg( sc.score ) 
FROM
	course c
	LEFT JOIN scores sc ON c.id = sc.c_id 
WHERE
	c.NAME = '数学';

10.将各科目按照平均分排序。


SELECT
	c.id,
	c.NAME,
	avg( sc.score ) score 
FROM
	course c
	LEFT JOIN scores sc ON c.id = sc.c_id 
GROUP BY
	c.id,
	c.NAME 
ORDER BY
	score DESC;

11.查询老师的信息和他所带的科目的平均分


SELECT
	t.id,
	t.NAME,
	c.id cid,
	c.NAME cname,
	avg( r.score ) 
FROM
	teacher t
	LEFT JOIN course c ON t.id = c.t_id
	LEFT JOIN scores r ON r.c_id = c.id 
GROUP BY
	t.id,
	t.NAME,
	c.id,
	c.NAME;

12.查询被"Tom"和"Jerry"教的课程的最高分和最低分


SELECT
	t.id,
	t.NAME,
	c.id cid,
	c.NAME cname,
	max( r.score ),
	min( r.score ) 
FROM
	teacher t
	LEFT JOIN course c ON t.id = c.t_id
	LEFT JOIN scores r ON r.c_id = c.id 
GROUP BY
	t.id,
	t.NAME,
	c.id,
	c.NAME 
HAVING
	t.NAME IN ( 'Tom', 'Jerry' );

13.查询每个学生的最好成绩的科目名称（子查询）


SELECT
	t.id,
	t.sname,
	r.c_id,
	c.NAME,
	t.score 
FROM
	(
	SELECT
		s.id,
		s.NAME sname,
		max( r.score ) score 
	FROM
		student s
		LEFT JOIN scores r ON r.s_id = s.id 
	GROUP BY
		s.id,
		s.NAME 
	) t
	LEFT JOIN scores r ON r.s_id = t.id 
	AND r.score = t.score
	LEFT JOIN course c ON r.c_id = c.id;

14.查询所有学生的课程及分数


SELECT
	s.id,
	s.NAME,
	c.id,
	c.NAME,
	r.score 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id
	LEFT JOIN course c ON c.id = r.c_id;

15.查询课程编号为1且课程成绩在60分以上的学生的学号和姓名（子查询）


SELECT
	s.*,
	r.* 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
WHERE
	r.c_id = 1 
	AND r.score > 60

16. 查询平均成绩大于等于70的所有学生学号、姓名和平均成绩


SELECT
	s.id,
	s.NAME,
	t.score 
FROM
	student s
	LEFT JOIN ( SELECT r.s_id, avg( r.score ) score FROM scores r GROUP BY r.s_id ) t ON s.id = t.s_id 
WHERE
	t.score >= 70;

17.查询有不及格课程的学生信息


SELECT
	* 
FROM
	student s 
WHERE
	id IN ( SELECT r.s_id FROM scores r GROUP BY r.s_id HAVING min( r.score ) < 60 );

18.查询每门课程有成绩的学生人数


SELECT
	c.id,
	c.NAME,
	count(*) 
FROM
	course c
	LEFT JOIN scores r ON c.id = r.c_id 
GROUP BY
	c.id,
	c.NAME;

19.查询每门课程的平均成绩，结果按照平均成绩降序排列，如果平均成绩相同，再按照课程编号升序排列


SELECT
	c.id,
	c.NAME,
	avg( score ) score 
FROM
	course c
	LEFT JOIN scores r ON c.id = r.c_id 
GROUP BY
	c.id,
	c.NAME 
ORDER BY
	score DESC,
	c.id ASC;

20.查询平均成绩大于60分的同学的学生编号和学生姓名和平均成绩


SELECT
	s.id,
	s.NAME sname,
	avg( r.score ) score 
FROM
	student s
	LEFT JOIN scores r ON r.s_id = s.id
	LEFT JOIN course c ON c.id = r.c_id 
GROUP BY
	s.id,
	s.NAME 
HAVING
	score > 65;

21.查询有且仅有一门课程成绩在80分以上的学生信息


SELECT
	s.id,
	s.NAME,
	s.gender 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
WHERE
	r.score > 80 
GROUP BY
	s.id,
	s.NAME,
	s.gender 
HAVING
	count(*) = 1;

22.查询出只有三门课程的学生的学号和姓名


SELECT
	s.id,
	s.NAME,
	s.gender 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
GROUP BY
	s.id,
	s.NAME,
	s.gender 
HAVING
	count(*) = 3;

23.查询有不及格课程的课程信息


SELECT
	* 
FROM
	course c 
WHERE
	id IN (
	SELECT
		r.c_id 
	FROM
		scores r 
	GROUP BY
		r.c_id 
	HAVING
	min( r.score ) < 60 
	);

24.查询至少选择4门课程的学生信息


SELECT
	s.id,
	s.NAME 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
GROUP BY
	s.id,
	s.NAME 
HAVING
	count(*) >= 4;

25.查询没有选全所有课程的同学的信息


SELECT
	* 
FROM
	student 
WHERE
	id IN (
	SELECT
		r.s_id 
	FROM
		scores r 
	GROUP BY
		r.s_id 
	HAVING
	count(*) != 5
	);

26.查询选全所有课程的同学的信息


SELECT
	s.id,
	s.NAME,
	count(*) number 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
GROUP BY
	s.id,
	s.NAME 
HAVING
	number = ( SELECT count(*) FROM course );

27.查询各学生都选了多少门课


SELECT
	s.id,
	s.NAME,
	count(*) number 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id 
GROUP BY
	s.id,
	s.NAME;

28.查询课程名称为"java"，且分数低于60分的学生姓名和分数


SELECT
	s.id,
	s.NAME,
	r.score 
FROM
	student s
	LEFT JOIN scores r ON s.id = r.s_id
	LEFT JOIN course c ON r.c_id = c.id 
WHERE
	c.NAME = 'java' 
	AND r.score < 60;

29.查询学过"Tony"老师授课的同学的信息


SELECT
	s.id,
	s.NAME 
FROM
	student s
	LEFT JOIN scores r ON r.s_id = s.id
	LEFT JOIN course c ON c.id = r.c_id
	LEFT JOIN teacher t ON t.id = c.t_id 
WHERE
	t.NAME = 'Tom';

30.查询没学过"Tony"老师授课的学生信息


SELECT
	* 
FROM
	student 
WHERE
	id NOT IN (
	SELECT DISTINCT
		s.id 
	FROM
		student s
		LEFT JOIN scores r ON r.s_id = s.id
		LEFT JOIN course c ON c.id = r.c_id
		LEFT JOIN teacher t ON t.id = c.t_id 
	WHERE
	t.NAME = 'Tom' 
	)

相关阅读:
MySQL 的数据目录
 细说Hash（哈希）
《上海悠悠接口自动化平台》-4.注册用例集实战演示
 基于ASP．NET的Web应用系统架构探讨
 世界上第一台个人电脑是哪台？
CSS过渡效果
 源码分析：数据 dao 层
 Web安全之CTF测试赛
 两名高管遭解雇，Twitter：只出不进
 【uni-app】uni-app编译运行，提示app.json:pages不能为空，怎么解决？
原文地址：https://blog.csdn.net/weixin_49627122/article/details/126380916