sql常见50道查询练习题

sql常见50道查询练习题

  • [1. 表创建](#1. 表创建)
    • [1.1 表创建](#1.1 表创建)
    • [1.2 数据插入](#1.2 数据插入)
  • [2. 简单查询例题(3题)](#2. 简单查询例题(3题))
    • [2.1 查询"李"姓老师的数量](#2.1 查询"李"姓老师的数量)
    • [2.2 查询男生、女生人数](#2.2 查询男生、女生人数)
    • [2.3 查询名字中含有"风"字的学生信息](#2.3 查询名字中含有"风"字的学生信息)
  • [3. 日期相关例题(6题)](#3. 日期相关例题(6题))
    • [3.1 查询各学生的年龄](#3.1 查询各学生的年龄)
    • [3.2 查询本周过生日的学生](#3.2 查询本周过生日的学生)
    • [3.3 查询下周过生日的学生](#3.3 查询下周过生日的学生)
    • [3.4 查询本月过生日的学生](#3.4 查询本月过生日的学生)
    • [3.5 查询下月过生日的学生](#3.5 查询下月过生日的学生)
    • [3.6 查询1990年出生的学生名单](#3.6 查询1990年出生的学生名单)
  • [4. 开窗函数查询(7题)](#4. 开窗函数查询(7题))
    • [4.1 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩](#4.1 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩)
    • [4.2 按各科成绩进行排序,并显示排名(实现不完全)](#4.2 按各科成绩进行排序,并显示排名(实现不完全))
    • [4.3 查询学生的总成绩并进行排名](#4.3 查询学生的总成绩并进行排名)
    • [4.4 查询所有课程的成绩第2名到第3名的学生信息及该课程成绩](#4.4 查询所有课程的成绩第2名到第3名的学生信息及该课程成绩)
    • [4.5 查询学生平均成绩及其名次](#4.5 查询学生平均成绩及其名次)
    • [4.6 查询各科成绩前三名的记录](#4.6 查询各科成绩前三名的记录)
    • [4.7 查询每门功成绩最好的前两名](#4.7 查询每门功成绩最好的前两名)
  • [5. 表连接+子查询+聚合函数查询(34题)](#5. 表连接+子查询+聚合函数查询(34题))
    • [5.1 查询"01"课程比"02"课程成绩高的学生的信息及课程分数](#5.1 查询"01"课程比"02"课程成绩高的学生的信息及课程分数)
    • [5.2 查询"01"课程比"02"课程成绩低的学生的信息及课程分数](#5.2 查询"01"课程比"02"课程成绩低的学生的信息及课程分数)
    • [5.3 查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩](#5.3 查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩)
    • [5.4 查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩(包括有成绩的和无成绩的)](#5.4 查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩(包括有成绩的和无成绩的))
    • [5.5 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩](#5.5 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩)
    • [5.6 查询学过"张三"老师授课的同学的信息](#5.6 查询学过"张三"老师授课的同学的信息)
    • [5.7 查询没学过"张三"老师授课的同学的信息](#5.7 查询没学过"张三"老师授课的同学的信息)
    • [5.8 查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息](#5.8 查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息)
    • [5.9 查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息](#5.9 查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息)
    • [5.10 查询没有学全所有课程的同学的信息](#5.10 查询没有学全所有课程的同学的信息)
    • [5.11 查询至少有一门课与学号为"01"的同学所学相同的同学的信息](#5.11 查询至少有一门课与学号为"01"的同学所学相同的同学的信息)
    • [5.12 查询和"01"号的同学学习的课程完全相同的其他同学的信息](#5.12 查询和"01"号的同学学习的课程完全相同的其他同学的信息)
    • [5.13 查询没学过"张三"老师讲授的任一门课程的学生姓名](#5.13 查询没学过"张三"老师讲授的任一门课程的学生姓名)
    • [5.14 查询两门及其以上不及格课程的同学的学号,姓名及其平均成绩](#5.14 查询两门及其以上不及格课程的同学的学号,姓名及其平均成绩)
    • [5.15 检索"01"课程分数小于60,按分数降序排列的学生信息](#5.15 检索"01"课程分数小于60,按分数降序排列的学生信息)
    • [5.16 查询各科成绩最高分、最低分和平均分](#5.16 查询各科成绩最高分、最低分和平均分)
    • [5.17 统计各科成绩各分数段人数](#5.17 统计各科成绩各分数段人数)
    • [5.18 查询不同老师所教不同课程平均分从高到低显示](#5.18 查询不同老师所教不同课程平均分从高到低显示)
    • [5.19 查询每门课程被选修的学生数](#5.19 查询每门课程被选修的学生数)
    • [5.20 查询出只有两门课程的全部学生的学号和姓名](#5.20 查询出只有两门课程的全部学生的学号和姓名)
    • [5.21 查询同名同性学生名单,并统计同名人数](#5.21 查询同名同性学生名单,并统计同名人数)
    • [5.22 查询每门课程的平均成绩](#5.22 查询每门课程的平均成绩)
    • [5.23 查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩](#5.23 查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩)
    • [5.24 查询课程名称为"数学",且分数低于60的学生姓名和分数](#5.24 查询课程名称为"数学",且分数低于60的学生姓名和分数)
    • [5.25 查询所有学生的课程及分数情况](#5.25 查询所有学生的课程及分数情况)
    • [5.26 查询任何一门课程成绩在70分以上的姓名、课程名称和分数(学生的每门课都大于70)](#5.26 查询任何一门课程成绩在70分以上的姓名、课程名称和分数(学生的每门课都大于70))
    • [5.27 查询不及格的课程](#5.27 查询不及格的课程)
    • [5.28 查询课程编号为01且课程成绩在80分以上的学生的学号和姓名](#5.28 查询课程编号为01且课程成绩在80分以上的学生的学号和姓名)
    • [5.29 求每门课程的学生人数](#5.29 求每门课程的学生人数)
    • [5.30 查询选修"张三"老师所授课程的学生中,成绩最高的学生信息及其成绩](#5.30 查询选修"张三"老师所授课程的学生中,成绩最高的学生信息及其成绩)
    • [5.31 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩](#5.31 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩)
    • [5.32 统计每门课程的学生选修人数(超过5人的课程才统计)](#5.32 统计每门课程的学生选修人数(超过5人的课程才统计))
    • [5.33 检索至少选修两门课程的学生学号](#5.33 检索至少选修两门课程的学生学号)
    • [5.34 查询选修了全部课程的学生信息](#5.34 查询选修了全部课程的学生信息)

1. 表创建

1.1 表创建

sql 复制代码
#--1.学生表 
#Student(s_id,s_name,s_birth,s_sex) --学生编号,学生姓名, 出生年月,学生性别
CREATE TABLE `Student` (
    `s_id` VARCHAR(20),
    s_name VARCHAR(20) NOT NULL DEFAULT '',
    s_brith VARCHAR(20) NOT NULL DEFAULT '',
    s_sex VARCHAR(10) NOT NULL DEFAULT '',
    PRIMARY KEY(s_id)
);

#--2.课程表 
#Course(c_id,c_name,t_id) -- --课程编号, 课程名称, 教师编号 
create table Course(
    c_id varchar(20),
    c_name VARCHAR(20) not null DEFAULT '',
    t_id VARCHAR(20) NOT NULL,
    PRIMARY KEY(c_id)
);

/*
--3.教师表 
Teacher(t_id,t_name) --教师编号,教师姓名 
*/
CREATE TABLE Teacher(
    t_id VARCHAR(20),
    t_name VARCHAR(20) NOT NULL DEFAULT '',
    PRIMARY KEY(t_id)
);

/*
--4.成绩表 
Score(s_id,c_id,s_score) --学生编号,课程编号,分数
*/
Create table Score(
    s_id VARCHAR(20),
    c_id VARCHAR(20) not null default '',
    s_score INT(3),
    primary key(`s_id`,`c_id`)
);

1.2 数据插入

sql 复制代码
#--插入学生表测试数据
#('01' , '赵雷' , '1990-01-01' , '男')
insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '1990-05-20' , '男');
insert into Student values('04' , '李云' , '1990-08-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-03-01' , '女');
insert into Student values('07' , '郑竹' , '1989-07-01' , '女');
insert into Student values('08' , '王菊' , '1990-01-20' , '女');

#--课程表测试数据
insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');

#--教师表测试数据
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');

#--成绩表测试数据
insert into Score values('01' , '01' , 80);
insert into Score values('01' , '02' , 90);
insert into Score values('01' , '03' , 99);
insert into Score values('02' , '01' , 70);
insert into Score values('02' , '02' , 60);
insert into Score values('02' , '03' , 80);
insert into Score values('03' , '01' , 80);
insert into Score values('03' , '02' , 80);
insert into Score values('03' , '03' , 80);
insert into Score values('04' , '01' , 50);
insert into Score values('04' , '02' , 30);
insert into Score values('04' , '03' , 20);
insert into Score values('05' , '01' , 76);
insert into Score values('05' , '02' , 87);
insert into Score values('06' , '01' , 31);
insert into Score values('06' , '03' , 34);
insert into Score values('07' , '02' , 89);
insert into Score values('07' , '03' , 98);

2. 简单查询例题(3题)

2.1 查询"李"姓老师的数量

sql 复制代码
SELECT
	count(1) as cnt
FROM
	teacher
WHERE
	t_name like "李%"

2.2 查询男生、女生人数

sql 复制代码
SELECT
	s.s_sex,
	count(1) as 人数
FROM
	student s
group by
	s.s_sex

2.3 查询名字中含有"风"字的学生信息

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	s_name like "%风%"

3. 日期相关例题(6题)

3.1 查询各学生的年龄

  • (按照出生日期来算,当前月日 < 出生年月的月日则,年龄减一)

    sql 复制代码
    -- if函数
    
    select
    	a.*,
    	year(NOW())-year(a.s_brith)-if(DATE_FORMAT(now(),"%m%d") >DATE_FORMAT(a.s_brith,"%m%d"),0,1) as age
    FROM
    	student a
    
    -- case函数
     
    select s_brith,
    	(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_brith,'%Y') - (case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_brith,'%m%d') then 0 else 1 end)) as age
    from student;

3.2 查询本周过生日的学生

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	WEEKOFYEAR(STR_TO_DATE(concat(year(NOW()),DATE_FORMAT(s_brith,'%m%d')),"%Y%m%d"))=WEEKOFYEAR(NOW())
-- 	WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)

3.3 查询下周过生日的学生

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	WEEKOFYEAR(STR_TO_DATE(concat(year(NOW()),DATE_FORMAT(s_brith,'%m%d')),"%Y%m%d"))=WEEKOFYEAR(NOW()+interval "7" day)
-- 	WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1=WEEK(s_birth)

3.4 查询本月过生日的学生

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	MONTH(now())=month(s_brith)

3.5 查询下月过生日的学生

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	MONTH(now()+interval "1" month)=month(s_brith)

3.6 查询1990年出生的学生名单

sql 复制代码
SELECT
	*
FROM
	student
WHERE
	s_brith like "1990%"
-- 	left(s_brith,4)="1990"
-- 	year(s_brith)="1990"

4. 开窗函数查询(7题)

4.1 按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

  • 方法一:开窗函数

    sql 复制代码
    select
    	a.*,
    	avg(a.s_score) over(PARTITION by a.s_id) as avg_score
    FROM
    	score a
  • 方法二:临时表连接

    sql 复制代码
    SELECT
    	a.*,
    	t.avg_score
    FROM
    	score a,
    	(SELECT
    		a.s_id,
    		round(avg(a.s_score),2) as avg_score
    	FROM
    		score a
    	group by
    		a.s_id) t
    WHERE
    	a.s_id=t.s_id
    order by
    	t.avg_score desc
  • 方法三:长型数据转为宽型数据

    sql 复制代码
    SELECT
    	a.s_id,
    	ifnull((select s_score from score where s_id=a.s_id and c_id="01"),0) as "语文",
    	ifnull((select s_score from score where s_id=a.s_id and c_id="02"),0) as "数学",
    	ifnull((select s_score from score where s_id=a.s_id and c_id="03"),0) as "英语",
    	ifnull(round(avg(a.s_score),2),0) as avg_score
    FROM
    	score a
    group by
    	a.s_id
    order by
    	ifnull(round(avg(a.s_score),2),0) desc

4.2 按各科成绩进行排序,并显示排名(实现不完全)

  • 方法一:开窗函数

    sql 复制代码
    SELECT
    	a.*,
    	rank() over(PARTITION by c_id order by s_score desc) rank排名,
    	row_number() over(PARTITION by c_id order by s_score desc) row_number排名,
    	dense_rank() over(PARTITION by c_id order by s_score desc) dense_rank排名
    FROM
    	score a
  • 方法二:子查询

    sql 复制代码
    SELECT	
    	a.*,
    	(select count(s_score) from score b where a.c_id=b.c_id and  a.s_score<b.s_score)+1 rk,
    	(select count(distinct s_score) from score b where a.c_id=b.c_id and  a.s_score<=b.s_score) den_rk
    FROM
    	score a
    order by
    	c_id,s_score desc

4.3 查询学生的总成绩并进行排名

  • 方法一:开窗函数

    sql 复制代码
    SELECT
    	t.*,
    	rank() over(order by sum_score desc) rank排名
    FROM
    	(SELECT
    		s_id,
    		sum(s_score) as sum_score
    	FROM
    		score
    	group by
    		s_id) t

4.4 查询所有课程的成绩第2名到第3名的学生信息及该课程成绩

  • 方法一:子查询+开窗函数

    sql 复制代码
    SELECT
    	a.*,
    	t.c_id,
    	t.rk,
    	t.s_score
    FROM
    	student a,
    	(SELECT
    		a.s_id,
    		a.c_id,
    		a.s_score,
    		dense_rank() over(PARTITION by a.c_id order by a.s_score desc) as rk
    	FROM
    		score a) t
    WHERE
    	t.rk in (2,3)
    AND
    	a.s_id=t.s_id

4.5 查询学生平均成绩及其名次

  • 方法一: 开窗函数

    sql 复制代码
    SELECT
    	t.*,
    	rank() over(order by t.avg_score desc) 排名
    FROM
    	(SELECT
    		a.s_id,
    		round(avg(a.s_score),2) as avg_score
    	FROM
    		score a
    	group by
    		a.s_id) t

4.6 查询各科成绩前三名的记录

  • 方法一:开窗函数

    sql 复制代码
    SELECT
    	t.*
    from
    	(SELECT
    		a.c_id,
    		a.c_name,
    		b.s_score,
    		rank() over(PARTITION by a.c_id order by b.s_score desc) rk
    	FROM
    		course a
    	LEFT JOIN
    		score b
    	ON
    		a.c_id=b.c_id) t
    WHERE
    	t.rk<=3;
  • 方法二:子查询

    sql 复制代码
    SELECT
    	*
    from (
    	SELECT
    		a.c_id,
    		a.c_name,
    		b.s_score,
    		(select count(c.s_score) from score c where a.c_id=c.c_id and b.s_score<c.s_score)+1 as rk
    	FROM
    		course a
    	LEFT JOIN
    		score b
    	ON
    		a.c_id=b.c_id) t
    WHERE
    	t.rk<=3
    order by
    	t.c_name,t.rk asc;

4.7 查询每门功成绩最好的前两名

  • 方法一:开窗函数

    sql 复制代码
    SELECT
    	t.s_id,
    	t.c_id,
    	t.s_score
    FROM
    	(SELECT
    		*,
    		rank() over(PARTITION by b.c_id order by b.s_score desc) rk
    	FROM
    		score b) t
    WHERE
    	t.rk<=2;
  • 方法二:自连接

    sql 复制代码
    SELECT
    	t.s_id,
    	t.c_id,
    	t.s_score
    FROM
    	(SELECT
    		a.*,
    		(select count(1) from score b where b.c_id=a.c_id and a.s_score<b.s_score)+1 as rk
    	FROM
    		score a
    	order by
    		a.c_id,rk) t
    WHERE	
    	t.rk<=2
  • 方法三:条件查询+子查询

    sql 复制代码
    SELECT
    	a.*
    FROM
    	score a
    WHERE
    	(select count(1) from score b where b.c_id=a.c_id and a.s_score<b.s_score)+1<=2
    order by
    	a.c_id

5. 表连接+子查询+聚合函数查询(34题)

5.1 查询"01"课程比"02"课程成绩高的学生的信息及课程分数

  • 方法一:自连接,同列比较,使用自查询

    • 思路:先找出查询条件的学生信息及分数,根据子查询得到最终结果
    sql 复制代码
    SELECT
    st.*,t1.sc1,t1.sc2
    FROM
     student st,
    	(SELECT
    		s1.s_id,s1.s_score as sc1,s2.s_score as sc2
    	FROM
    		score s1,score s2
    	WHERE	
    		s1.c_id="01"
    	AND	
    		s2.c_id="02"
    	AND
    		s1.s_id=s2.s_id
    	AND
    		s1.s_score>s2.s_score) t1
    WHERE
    	st.s_id=t1.s_id;
  • 方法二:表连接

    sql 复制代码
    SELECT
    st.*,s1.s_score as sc1,s2.s_score as sc2
    FROM
    	student st
    left JOIN
    	score s1
    ON
    	s1.s_id=st.s_id
    left JOIN
    	score s2
    ON
    	s2.s_id=st.s_id
    WHERE	
    	s1.c_id="01"
    AND	
    	s2.c_id="02"
    AND
    	s1.s_id=s2.s_id
    AND
    	s1.s_score>s2.s_score
  • 数据长型数据变为宽型数据

    sql 复制代码
    -- IF函数或case函数
    SELECT
    	a.*,
    	t.s01,
    	t.s02
    from
    	student a,
    	(SELECT
    		a.s_id,
    		max(case when a.c_id="01" then a.s_score end) as s01,
    		max(case when a.c_id="02" then a.s_score end) as s02
    --  max(if(a.c_id="01",a.s_score,null)) as s01,
    --  max(if(a.c_id="02",a.s_score,null)) as s02
    	from
    		score a
    	group by
    		a.s_id) t
    WHERE
    	a.s_id=t.s_id
    AND
    	t.s01>t.s02

5.2 查询"01"课程比"02"课程成绩低的学生的信息及课程分数

  • 与上一题思路一致,条件大于变小于

  • 方法一:自连接

    sql 复制代码
    SELECT
    st.*,t1.sc1,t1.sc2
    FROM
     student st,
    	(SELECT
    		s1.s_id,s1.s_score as sc1,s2.s_score as sc2
    	FROM
    		score s1,score s2
    	WHERE	
    		s1.c_id="01"
    	AND	
    		s2.c_id="02"
    	AND
    		s1.s_id=s2.s_id
    	AND
    		s1.s_score<s2.s_score) t1
    WHERE
    	st.s_id=t1.s_id;
  • 方法二:表连接

    sql 复制代码
    SELECT
    	st.*,s1.s_score as sc1,s2.s_score as sc2
    FROM
    	student st
    left JOIN
    	score s1
    ON
    	s1.s_id=st.s_id
    left JOIN
    	score s2
    ON
    	s2.s_id=st.s_id
    WHERE	
    	s1.c_id="01"
    AND	
    	s2.c_id="02"
    AND
    	s1.s_id=s2.s_id
    AND
    	s1.s_score<s2.s_score
    	
    -- 方法二
    SELECT
    	st.*,s1.s_score as sc1,s2.s_score as sc2
    FROM
    	student st
    left JOIN
    	score s1
    ON
    	s1.s_id=st.s_id
    AND
    	s1.c_id="01"
    left JOIN
    	score s2
    ON
    	s2.s_id=st.s_id
    AND
    	s2.c_id="02"
    AND
    	s1.s_id=s2.s_id
    WHERE
    	s1.s_score<s2.s_score
  • 方法三:数据长型数据变为宽型数据

    sql 复制代码
    -- IF函数或case函数
    SELECT
    	a.*,
    	t.s01,
    	t.s02
    from
    	student a,
    	(SELECT
    		a.s_id,
    		max(case when a.c_id="01" then a.s_score end) as s01,
    		max(case when a.c_id="02" then a.s_score end) as s02
    --  max(if(a.c_id="01",a.s_score,null)) as s01,
    --  max(if(a.c_id="02",a.s_score,null)) as s02
    	from
    		score a
    	group by
    		a.s_id) t
    WHERE
    	t.s01<t.s02
    AND
    	a.s_id=t.s_id

5.3 查询平均成绩大于等于60分的同学的学生编号和学生姓名和平均成绩

  • 方法一:子查询

    sql 复制代码
    -- 子查询一
    SELECT
    st.s_id,st.s_name,t.avg_s
    FROM
    	student ST,
    	(SELECT
    		s.s_id,round(avg(s.s_score),2) as avg_s
    	FROM	
    		score s
    	GROUP BY
    		s.s_id
    	HAVING
    		round(avg(s.s_score),2)>=60) t
    WHERE
    	st.s_id=t.s_id
    
    -- 方法二:子查询二
    
    SELECT
    	s.s_id,
    	(select s_name from student where s_id=s.s_id) as s_name,
    	round(avg(s.s_score),2) as avg_s
    FROM	
    	score s
    GROUP BY
    	s.s_id
    HAVING
    	avg_s>=60
  • 方法二:表连接

    sql 复制代码
    SELECT
    	a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    GROUP BY
    	a.s_id
    HAVING
    	round(avg(b.s_score),2)>=60;

5.4 查询平均成绩小于60分的同学的学生编号和学生姓名和平均成绩(包括有成绩的和无成绩的)

  • 方法一:子查询

    sql 复制代码
    -- 有成绩的
    
    SELECT
    	a.s_id,a.s_name,t.avg_acore
    FROM
    	student a,
    	(SELECT
    		a.s_id,round(avg(a.s_score),2) as avg_acore
    	FROM
    		score a
    	GROUP BY
    		a.s_id
    	HAVING
    		round(avg(a.s_score),2)<60) t
    WHERE
    	a.s_id=t.s_id
     
    UNION
    -- 没有成绩的:没有成绩的s_id不存在
    SELECT
    	a.s_id,a.s_name,0 as avg_acore
    FROM
    	student a
    WHERE
    	a.s_id not in (SELECT DISTINCT s_id FROM score);
  • 方法二:表连接

    sql 复制代码
    SELECT
    	a.s_id,a.s_name,ifnull(round(avg(b.s_score),2),0) as avg_score
    FROM
    	student a
    LEFT JOIN
    	score b
    on 
    	a.s_id=b.s_id
    GROUP BY
    	a.s_id
    HAVING
    	avg_score<60

5.5 查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩

sql 复制代码
SELECT
	a.s_id,
	a.s_name,
	count(b.c_id) as cnt_course,
	ifnull(sum(b.s_score),0) as sum_score
FROM
	student a
LEFT JOIN
	score b
ON
	a.s_id=b.s_id
group by
	a.s_id

5.6 查询学过"张三"老师授课的同学的信息

  • 方法一:表连接+子查询单层嵌套

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a
    LEFT JOIN
    	score b
    on 
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	b.c_id=c.c_id
    where c.t_id in(SELECT t_id FROM teacher WHERE t_name = "张三")
  • 方法二:表连接+子查询多层嵌套

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    WHERE
    	b.c_id in (
    SELECT
    	c_id
    FROM
    	course where t_id in(SELECT t_id from teacher where t_name="张三")
    );
  • 方法三:多表连接

    sql 复制代码
    select
    	a.*
    from
    	student a,score b,course c,teacher d
    WHERE
    	a.s_id=b.s_id
    AND
    	b.c_id=c.c_id
    AND
    	c.t_id=d.t_id
    AND
    	d.t_name="张三"

5.7 查询没学过"张三"老师授课的同学的信息

  • 注意:一个学生有几门课程包含张三课程,不是张三课程的,根据没学过的查询不出来,因为一个人有多个老师的课程

  • 方法一:多层嵌套子查询

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s
    WHERE
    	s.s_id NOT IN (
    		-- 查找学的学生
    		SELECT DISTINCT
    			a.s_id
    		FROM
    			student a
    		LEFT JOIN score b ON a.s_id = b.s_id
    		WHERE
    			b.c_id IN (
    				-- 查找学过的课程
    				SELECT c_id
    				FROM course
    				WHERE t_id IN ( SELECT t_id FROM teacher WHERE t_name = "张三")
    			)
    	)
  • 方法二:条件查询+子表连接

    sql 复制代码
    SELECT
    	*
    FROM
    	student s
    WHERE
    	s.s_id not in (
    				select
    					a.s_id
    				from
    					score a,
    					course b,
    					teacher c
    				WHERE
    					a.c_id=b.c_id
    				AND
    					b.t_id=c.t_id
    				AND
    					c.t_name="张三")

5.8 查询学过编号为"01"并且也学过编号为"02"的课程的同学的信息

  • 方法一:子查询+自连接,同列对比可以用自连接

    sql 复制代码
    SELECT
    	*
    FROM
    	student s
    WHERE
    	s.s_id in(
    					SELECT
    						a.s_id
    					FROM
    						score a,score b
    					WHERE
    						a.c_id="01" 
    					AND
    						b.c_id="02"
    					AND
    						a.s_id=b.s_id)
  • 方法二:连表+自连接,同列对比可以用自连接

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s
    LEFT JOIN 
    	score a
    ON
    	s.s_id=a.s_id
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    WHERE
    	a.c_id="01" 
    AND
    	b.c_id="02"
  • 方法三:条件查询+子查询

    sql 复制代码
    SELECT
    	*
    FROM
    	student
    WHERE
    	s_id in (SELECT
    					s_id
    				FROM
    					score
    				where
    					c_id="01" or c_id="02"
    				GROUP BY
    					s_id
    				HAVING
    					count(1)=2)
  • 方法四:自连接,条件连接

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s,score a,score b
    WHERE
    	s.s_id=a.s_id
    AND
    	a.s_id=b.s_id
    AND
    	a.c_id="01" 
    AND
    	b.c_id="02"
  • 方法五:子查询+数据长型数据变为宽型数据

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a,
    	(select
    		a.s_id,
    		max(if(a.c_id="01",a.s_score,0)) as s01,
    		max(if(a.c_id="02",a.s_score,0)) as s02
    	from
    		score a
    	group by
    		a.s_id) t
    WHERE
    	a.s_id=t.s_id
    AND
    	t.s01>0
    AND
    	t.s02>0

5.9 查询学过编号为"01"但是没有学过编号为"02"的课程的同学的信息

  • 方法一:条件查询+子查询

    sql 复制代码
    select
    	a.*
    from
    	student a
    WHERE	
    	a.s_id in(select s_id from score where c_id="01") 
    AND
    	a.s_id not in (select s_id from score where c_id="02")
  • 方法二: 子查询+分组聚合

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s,
    	(
    		SELECT
    			a.s_id,
    			max(case when a.c_id="01" then a.s_score end) s01,
    			max(case when a.c_id="02" then a.s_score end) s02
    		FROM
    			score a
    		group by
    			a.s_id) t
    WHERE
    	s.s_id=t.s_id
    AND
    	t.s01 is not NULL
    AND
    	t.s02 is null
  • 方法三:数据长型数据变为宽型数据

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a,
    	(select
    		a.s_id,
    		max(if(a.c_id="01",a.s_score,null)) as s01,
    		max(if(a.c_id="02",a.s_score,null)) as s02
    	from
    		score a
    	group by
    		a.s_id) t
    WHERE
    	a.s_id=t.s_id
    AND
    	t.s01 is not null
    AND
    	t.s02 is null

5.10 查询没有学全所有课程的同学的信息

  • 方法一:条件查询+子查询

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s
    WHERE
    	s.s_id in(
    			SELECT
    				a.s_id
    			FROM
    				score a
    			group by
    				a.s_id
    			having
    				count(1)<(select count(1) from course))
  • 方法二:表连接

    sql 复制代码
    SELECT
    	s.*,
    	count(a.c_id) cnt
    FROM
    	student s
    LEFT JOIN
    	score a
    ON
    	a.s_id=s.s_id
    group by
    	s.s_id
    HAVING
    	count(a.c_id)<(select count(1) from course)

5.11 查询至少有一门课与学号为"01"的同学所学相同的同学的信息

  • 方法一:子查询

    sql 复制代码
    SELECT
    	s.*
    FROM
    	student s
    WHERE
    	s.s_id in(
    			SELECT
    				distinct a.s_id
    			FROM
    				score a
    			WHERE
    				a.c_id in(
    						SELECT
    							b.c_id
    						FROM
    							score b
    						WHERE
    							b.s_id="01"))
    AND
    	s.s_id!='01'
  • 方法二:表连接+子查询

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a
    LEFT JOIN
    	score b
    on 
    	a.s_id=b.s_id
    WHERE
    	b.c_id in (
    			SELECT
    				b.c_id
    			FROM
    				score b
    			WHERE
    				b.s_id="01")
    group by 1,2,3,4

5.12 查询和"01"号的同学学习的课程完全相同的其他同学的信息

  • 筛选课程与01号一样的数据,计算课程数与01一致的
sql 复制代码
SELECT
	s.*
FROM
	student s
WHERE
	s.s_id in(
					SELECT distinct 
						a.s_id
					FROM
						score a
					WHERE
						a.c_id in(
								SELECT
									a.c_id
								FROM
									score a
								WHERE
									a.s_id="01")
					AND
						a.s_id!="01"
					group by 
						a.s_id
					HAVING
						count(distinct a.c_id)=(select count(1) from score a where a.s_id="01")
					)

5.13 查询没学过"张三"老师讲授的任一门课程的学生姓名

  • 查询学过张三老师的学生,在学生表中反向查询
sql 复制代码
SELECT
	s.s_name
FROM
	student s
WHERE
	s.s_id not in(
				SELECT
					a.s_id
				FROM
					score a
				WHERE
					a.c_id in (
							SELECT
								a.c_id
							FROM
								course a
							WHERE
								a.t_id in (SELECT t.t_id FROM teacher t WHERE t.t_name="张三")))

5.14 查询两门及其以上不及格课程的同学的学号,姓名及其平均成绩

  • 方法一:表连接+分组+having条件

    sql 复制代码
    SELECT
    	a.s_id,
    	a.s_name,
    	round(avg(b.s_score),2) as avg_score
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    group by
    	a.s_id
    having
    	sum(if(b.s_score>=60,0,1))>=2
  • 方法二:自连接+子查询

    sql 复制代码
    select
    	a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score
    FROM
    	student a,score b
    WHERE
    	a.s_id=b.s_id
    AND
    	a.s_id in(
    			SELECT
    				a.s_id
    			FROM
    				score a
    			WHERE
    				a.s_score<60
    			group by
    				a.s_id
    			HAVING
    				count(1)>=2)
    group by
    	a.s_id
  • 方法三:表连接+子查询

    sql 复制代码
    select
    	a.s_id,a.s_name,round(avg(b.s_score),2) as avg_score
    FROM
    	student a
    LEFT JOIN
    	score b
    on
    	a.s_id=b.s_id
    where
    	a.s_id in(
    			SELECT
    				a.s_id
    			FROM
    				score a
    			WHERE
    				a.s_score<60
    			group by
    				a.s_id
    			HAVING
    				count(1)>=2)
    group by
    	a.s_id

5.15 检索"01"课程分数小于60,按分数降序排列的学生信息

  • 方法一:表连接

    sql 复制代码
    SELECT
    	a.*,b.c_id,b.s_score
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    WHERE
    	b.c_id="01" and b.s_score<60
    order by
    	b.s_score desc

5.16 查询各科成绩最高分、最低分和平均分

  • 以如下形式显示:课程ID,课程name,最高分,最低分,平均分,及格率,中等率,优良率,优秀率

  • 及格为>=60,中等为:70-80,优良为:80-90,优秀为:>=90

  • 方法一:if语句

    sql 复制代码
    SELECT
    	a.c_id,
    	a.c_name,
    	max(b.s_score) as max_score,
    	min(b.s_score) as min_score,
    	round(avg(b.s_score),2) as avg_score,
    	round(100*sum(if(b.s_score>=60,1,0))/count(1),2) as "及格率",
    	round(100*sum(if(b.s_score>=70 and b.s_score<80,1,0))/count(1),2) as "中等率",
    	round(100*sum(if(b.s_score>=80 and b.s_score<90,1,0))/count(1),2) as "优良率",
    	round(100*sum(if(b.s_score>=90,1,0))/count(1),2) as "优秀率"
    FROM
    	course a,
    	score b
    WHERE
    	a.c_id=b.c_id
    group by
    	a.c_id
  • 方法二:case when

    sql 复制代码
    SELECT
    	a.c_id,
    	a.c_name,
    	max(b.s_score) as max_score,
    	min(b.s_score) as min_score,
    	round(avg(b.s_score),2) as avg_score,
    	round(100*sum(case when b.s_score>=60 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as "及格率",
    	round(100*sum(case when b.s_score>=70 and b.s_score<80 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as "中等率",
    	round(100*sum(case when b.s_score>=80 and b.s_score<90 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as "优良率",
    	round(100*sum(case when b.s_score>=90 then 1 else 0 end)/sum(case when b.s_score then 1 else 0 end),2) as "优秀率"
    FROM
    	course a,
    	score b
    WHERE
    	a.c_id=b.c_id
    group by
    	a.c_id

5.17 统计各科成绩各分数段人数

  • 课程编号,课程名称,[100-85],[85-70],[70-60],[0-60]个数及所占百分比

  • 方法一:if函数

    sql 复制代码
    SELECT
    	b.c_id,
    	a.c_name,
        round(100*sum(if(b.s_score>85 and b.s_score<=100,1,0))/count(1),2) as "[100-85]百分比",
    	sum(if(b.s_score>85 and b.s_score<=100,1,0)) as "[100-85]",
    	round(100*sum(if(b.s_score>70 and b.s_score<=85,1,0))/count(1),2) as "[85-70]百分比",
    	sum(if(b.s_score>70 and b.s_score<=85,1,0)) as "[85-70]",
    	round(100*sum(if(b.s_score>60 and b.s_score<=70,1,0))/count(1),2) as "[70-60]百分比",
    	sum(if(b.s_score>60 and b.s_score<=70,1,0)) as "[70-60]",
    	round(100*sum(if(b.s_score>0 and b.s_score<=60,1,0))/count(1),2) as "[0-60]百分比",
    	sum(if(b.s_score>=0 and b.s_score<=60,1,0)) as "[0-60]"
    FROM
    	course a,
    	score b
    WHERE
    	a.c_id=b.c_id
    group by
    	b.c_id

5.18 查询不同老师所教不同课程平均分从高到低显示

  • 方法一:表连接

    sql 复制代码
    SELECT
    	c.t_name,
    	a.c_name,
    	round(avg(b.s_score),2) as avg_score
    FROM
    	course a
    left JOIN
    	score b
    ON
    	a.c_id=b.c_id
    LEFT JOIN
    	teacher c
    ON
    	a.t_id=c.t_id
    group by
    	c.t_name,a.c_name
    order by
    	avg_score DESC

5.19 查询每门课程被选修的学生数

sql 复制代码
SELECT
	a.c_id,
	a.c_name,
	count(1) as cnt
FROM
	course a
LEFT JOIN
	score b
ON	
	a.c_id=b.c_id
group by
	a.c_id

5.20 查询出只有两门课程的全部学生的学号和姓名

  • 方法一:连表

    sql 复制代码
    SELECT
    	distinct a.s_id,a.s_name
    FROM
    	student a,
    	score b
    WHERE
    	a.s_id=b.s_id
    group by
    	a.s_id
    HAVING
    	count(b.c_id)=2
  • 方法二:条件查询

    sql 复制代码
    select 
    	s_id,
    	s_name 
    from 
    	student 
    where 
    	s_id in (select s_id from score GROUP BY s_id HAVING COUNT(c_id)=2);

5.21 查询同名同性学生名单,并统计同名人数

  • 方法一:分组条件查询

    sql 复制代码
    SELECT
    	s_name,
    	count(1) as "人数"
    FROM
    	student
    group by
    	s_name,s_sex
    HAVING
    	count(1)>1
  • 方法二:自连接(同列比较可以用自连接)

    sql 复制代码
    select 
    	a.s_name,
    	a.s_sex,
    	count(*) 
    from 
    	student a  
    JOIN 
    	student b 
    on 
    	a.s_id !=b.s_id 
    and 
    	a.s_name = b.s_name 
    and 
    	a.s_sex = b.s_sex
    GROUP BY 
    	a.s_name,a.s_sex

5.22 查询每门课程的平均成绩

  • 结果按平均成绩降序排列,平均成绩相同时,按课程编号升序排列

    sql 复制代码
    SELECT
    	a.c_id,
    	round(avg(a.s_score),2) as avg_score
    FROM
    	score a
    group by
    	a.c_id
    order by
    	avg_score desc,a.c_id asc	

5.23 查询平均成绩大于等于85的所有学生的学号、姓名和平均成绩

  • 方法一:子查询

    sql 复制代码
    SELECT
    	a.s_id,
    	a.s_name,
    	t.avg_score
    FROM
    	student a,
    	(SELECT
    		a.s_id,
    		round(avg(a.s_score),2) as avg_score
    	FROM
    		score a
    	group by
    		a.s_id
    	HAVING
    		avg_score>=85) t
    WHERE	
    	a.s_id=t.s_id
    AND
    	t.avg_score is not null
  • 方法二:表连接

    sql 复制代码
    select
    	a.s_id,
    	b.s_name,
    	ifnull(round(avg(a.s_score),2),0) as avg_score
    FROM
    	score a
    LEFT JOIN
    	student b
    ON
    	a.s_id=b.s_id
    GROUP BY
    	a.s_id
    HAVING
    	avg_score>=85

5.24 查询课程名称为"数学",且分数低于60的学生姓名和分数

  • 方法一:条件查询+子查询

    sql 复制代码
    SELECT
    	b.s_name,
    	a.s_score
    FROM
    	score a
    LEFT JOIN
    	student b
    ON
    	a.s_id=b.s_id
    WHERE
    	c_id in (SELECT c_id FROM course where c_name="数学")
    AND
    	a.s_score<60
  • 方法二:多表连接

    sql 复制代码
    SELECT
    	b.s_name,
    	a.s_score
    FROM
    	score a
    LEFT JOIN
    	student b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	a.c_id=c.c_id
    WHERE
    	c.c_name="数学"
    AND
    	a.s_score<60

5.25 查询所有学生的课程及分数情况

  • 方法一:表连接

    sql 复制代码
    SELECT
    	a.s_name,c.c_name,b.s_score
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
  • 方法二:if函数

    sql 复制代码
    SELECT
    	a.s_id,
    	a.s_name,
    	sum(if(c.c_name="语文",b.s_score,0)) as "语文",
    	sum(if(c.c_name="数学",b.s_score,0)) as "数学",
    	sum(if(c.c_name="英语",b.s_score,0)) as "英语",
    	sum(b.s_score) as "总分"
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
    group by
    	a.s_id,a.s_name
  • 方法三:case函数

    sql 复制代码
    select
    	a.s_id,
    	a.s_name,
    	sum(case when c.c_name="语文" then b.s_score else 0 end) as "语文",
    	sum(case when c.c_name="数学" then b.s_score else 0 end) as "数学",
    	sum(case when c.c_name="英语" then b.s_score else 0 end) as "英语",
    	sum(b.s_score) as "总分"
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
    group by
    	a.s_id,a.s_name

5.26 查询任何一门课程成绩在70分以上的姓名、课程名称和分数(学生的每门课都大于70)

  • 方法一:表连接+子查询

    sql 复制代码
    SELECT
    	a.s_name,
    	c.c_name,
    	b.s_score
    
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
    WHERE
    	a.s_id in (select s_id from score group by s_id having min(s_score)>70);

5.27 查询不及格的课程

  • 方法一:表连接
sql 复制代码
SELECT
distinct
	b.s_id,
	b.c_id,
	a.c_name,
	b.s_score
from
	course a
LEFT JOIN
	score b
ON
	a.c_id=b.c_id
WHERE
	b.s_score<60

5.28 查询课程编号为01且课程成绩在80分以上的学生的学号和姓名

  • 方法一:子查询

    sql 复制代码
    SELECT
    	t.s_id,
    	t.s_name
    FROM
    	student t
    WHERE
    	t.s_id in(
    			SELECT
    				a.s_id
    			FROM
    				score a
    			WHERE
    				a.c_id="01" 
    			AND
    				a.s_score>80)
  • 方法二:表连接

    sql 复制代码
    select
    	a.s_id,
    	a.s_name
    from
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    WHERE
    	b.c_id="01"
    AND
    	b.s_score>80

5.29 求每门课程的学生人数

sql 复制代码
SELECT
	a.c_name,
	count(1) as "人数"
FROM
	course a
LEFT JOIN
	score b
ON
	a.c_id=b.c_id
group by
	a.c_id

5.30 查询选修"张三"老师所授课程的学生中,成绩最高的学生信息及其成绩

  • 方法一:表连接+子查询

    sql 复制代码
    SELECT
    	a.*,
    	b.s_score as max_score,
    	b.c_id,
    	c.c_name
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
    WHERE
    -- 查询id
    	b.c_id in (
    						SELECT
    							c_id
    						FROM
    							course 
    						WHERE
    							t_id in (select t_id from teacher where t_name="张三")
    						)
    AND
    -- 查询最大分数
    	b.s_score=(select distinct max(s_score) from score where c_id="02")
  • 方法二:表连接

    sql 复制代码
     SELECT
    	a.*,
    	b.s_score as max_score,
    	b.c_id,
    	c.c_name
    FROM
    	student a
    LEFT JOIN
    	score b
    ON
    	a.s_id=b.s_id
    LEFT JOIN
    	course c
    ON
    	c.c_id=b.c_id
    LEFT JOIN
    	teacher d
    ON
    	d.t_id=c.t_id
    WHERE
    	d.t_name="张三"
    order by
    	max_score desc
    limit 1;

5.31 查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

sql 复制代码
SELECT
distinct
	a.*
FROM
	score a,
	score b
WHERE
	a.c_id!=b.c_id
AND
	a.s_score=b.s_score

5.32 统计每门课程的学生选修人数(超过5人的课程才统计)

  • 要求输出课程号和选修人数,查询结果按人数降序排列,若人数相同,按课程号升序排列

  • 方法一: 分组聚合

    sql 复制代码
    SELECT
    	c_id,
    	count(1) as "选修人数"
    FROM
    	score
    group by
    	c_id
    HAVING
    	count(1) >5
    order by
    	"选修人数" desc,c_id asc
  • 方法二:连表+分组聚合

    sql 复制代码
    SELECT
    	a.c_id,
    	count(b.s_id) cnt
    FROM
    	course a
    LEFT JOIN
    	score b
    ON
    	a.c_id=b.c_id
    group by
    	a.c_id
    HAVING
    	count(b.s_id)>5
    order by
    	cnt desc,a.c_id asc

5.33 检索至少选修两门课程的学生学号

sql 复制代码
SELECT
	s_id
FROM
	score
group by
	s_id
HAVING
	count(c_id)>=2;
    

5.34 查询选修了全部课程的学生信息

  • 方法一:连表查询

    sql 复制代码
    SELECT
    	a.*
    FROM
    	student a,
    	score b
    WHERE
    	a.s_id=b.s_id
    group by
    	s_id
    HAVING
    	count(1)=(select count(1) from course)
  • 方法二:子查询

    sql 复制代码
    SELECT
    	*
    FROM
    	student a
    WHERE
    	a.s_id in(
    		   select 
    				s_id
    			FROM
    				score
    			group by
    				s_id
    			HAVING	
    				count(1)=(select count(1) from course))
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