sql常见50道查询练习题

sql常见50道查询练习题

• 1. 表创建
• • 1.1 表创建
  • 1.2 数据插入
• 2. 简单查询例题(3题）
• • 2.1 查询"李"姓老师的数量
  • 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
• 3. 日期相关例题(6题）
• • 3.1 查询各学生的年龄
  • 3.2 查询本周过生日的学生
  • 3.3 查询下周过生日的学生
  • 3.4 查询本月过生日的学生
  • 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
• 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
  • 4.2 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
  • 4.4 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
  • 4.6 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
• 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
  • 5.2 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
  • 5.4 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
  • 5.6 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
  • 5.8 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
  • 5.10 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
  • 5.12 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
  • 5.14 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
  • 5.16 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
  • 5.18 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
  • 5.20 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
  • 5.22 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
  • 5.24 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
  • 5.26 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
  • 5.28 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
  • 5.30 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
  • 5.32 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
  • 5.34 查询选修了全部课程的学生信息

1. 表创建

1.1 表创建

#–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

#--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

SELECT
count(1) as cnt
FROM
teacher
WHERE
t_name like "李%"

2.2 查询男生、女生人数

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

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)

  -- 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

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

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

SELECT
*
FROM
student
WHERE
MONTH(now())=month(s_brith)

3.5 查询下月过生日的学生

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

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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

    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

  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

  -- 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

  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

  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

  -- 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

  -- 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

  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

  -- 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

  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

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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

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

  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

  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

  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）

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

  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

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

  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

   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

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

  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

  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

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

  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

  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))
  

原文地址：https://blog.csdn.net/web18285482512/article/details/144317528

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