经典50道SQL题目

最近觉得 JPA 用的太多了，全是 Java 代码里写查询，感觉对 SQL 有点生疏，恰好发现了这个经典的 SQL 练习题，题目来源SQL50 题

• sql 准备如下

create table course(
    id   varchar(10)                 null,
    name varchar(10) charset utf8mb3 null,
    tId  varchar(10)                 null);
create table student(
  	id  varchar(10),
  	name varchar(10),
  	age datetime,
  	sex varchar(10));
create table teacher(
  id varchar(10),
  name varchar(10));
create table sc(
  	sid varchar(10),
  	cid varchar(10),
  	score decimal(18,1));
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('09' , '张三' , '2017-12-20' , '女');
insert into student values('10' , '李四' , '2017-12-25' , '女');
insert into student values('11' , '李四' , '2017-12-30' , '女');
insert into student values('12' , '赵六' , '2017-01-01' , '女');
insert into student values('13' , '孙七' , '2018-01-01' , '女');
insert into course values('01' , '语文' , '02');
insert into course values('02' , '数学' , '01');
insert into course values('03' , '英语' , '03');
insert into teacher values('01' , '张三');
insert into teacher values('02' , '李四');
insert into teacher values('03' , '王五');
insert into sc values('01' , '01' , 80);
insert into sc values('01' , '02' , 90);
insert into sc values('01' , '03' , 99);
insert into sc values('02' , '01' , 70);
insert into sc values('02' , '02' , 60);
insert into sc values('02' , '03' , 80);
insert into sc values('03' , '01' , 80);
insert into sc values('03' , '02' , 80);
insert into sc values('03' , '03' , 80);
insert into sc values('04' , '01' , 50);
insert into sc values('04' , '02' , 30);
insert into sc values('04' , '03' , 20);
insert into sc values('05' , '01' , 76);
insert into sc values('05' , '02' , 87);
insert into sc values('06' , '01' , 31);
insert into sc values('06' , '03' , 34);
insert into sc values('07' , '02' , 89);
insert into sc values('07' , '03' , 98);

1、查询” 01 “课程比” 02 “课程成绩高的学生的信息及课程分数

查询同时存在” 01 “课程和” 02 “课程的情况

查询存在” 01 “课程但可能不存在” 02 “课程的情况(不存在时显示为 null )

查询不存在” 01 “课程但存在” 02 “课程的情况

2、 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

3、查询在 SC 表存在成绩的学生信息

4、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(没成绩的显示为 null )

查有成绩的学生信息

5、查询「李」姓老师的数量

6、查询学过「张三」老师授课的同学的信息

7、查询没有学全所有课程的同学的信息

8、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

9、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

10、查询没学过”张三”老师讲授的任一门课程的学生姓名

11、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

12、检索” 01 “课程分数小于 60，按分数降序排列的学生信息

13、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

14、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
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

15、按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

按各科成绩进行排序，并显示排名， Score 重复时合并名次

16、查询学生的总成绩，并进行排名，总分重复时保留名次空缺

查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

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]，[60-0] 及所占百分比

18、查询各科成绩前三名的记录

19、查询每门课程被选修的学生数

20、查询出只选修两门课程的学生学号和姓名

21、查询男生、女生人数

22、查询名字中含有「风」字的学生信息

23、查询同名同性学生名单，并统计同名人数

24、查询 1990 年出生的学生名单

25、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

26、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

27、查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

28、查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

29、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

30、查询不及格的课程

31、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

32、求每门课程的学生人数

33、成绩不重复，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

34、成绩有重复的情况下，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

35、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

36、查询每门功成绩最好的前两名

37、统计每门课程的学生选修人数（超过 5 人的课程才统计）

38、检索至少选修两门课程的学生学号

39、查询选修了全部课程的学生信息

40、查询各学生的年龄，只按年份来算

41、按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

42、查询本周过生日的学生

43、查询下周过生日的学生

44、查询本月过生日的学生

45、查询下月过生日的学生

# 1、查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
# 重点是先查出学生的id，通过sId内连接
select a.sId
from (select * from sc where cId = '01') a
         INNER JOIN
         (select * from sc where cId = '02') b
         on a.sId = b.sId
where a.score > b.score
group by a.sId;

# 通过id查询，这部分就比较简单了
select s.*, c.cId, c.score
from student s
         left join sc c on s.id = c.sId
where s.id in (select a.sId
               from (select * from sc where cId = '01') a
                        INNER JOIN (select * from sc where cId = '02') b
                                   on a.sId = b.sId
               where a.score > b.score
               group by a.sId);

SELECT student.*, 01_score.cId, 1_score, 02_score.cId, 2_score
FROM student
         JOIN (SELECT sId, cId, score AS 1_score
               FROM sc
               WHERE cId = '01') AS 01_score
              ON student.id = 01_score.sId
         JOIN (SELECT sId, cId, score AS 2_score
               FROM sc
               WHERE cId = '02') AS 02_score
              ON 01_score.sId = 02_score.sId
WHERE 1_score > 2_score;

# 2、平均成绩大于60的学生的编号和姓名和成绩
# 我自己写的答案
select s.id, s.name, idAndSc.avgs
from student s
         inner join (select sc.sId, avg(sc.score) avgs
                     from sc
                     group by sc.sId
                     having avgs >= 60) idAndSc on s.id = idAndSc.sId;

# 网上答案
select a.sId, b.name, avgs
from (select sId,
             AVG(score) as avgs
      from sc
      group by sId
      having AVG(score) >= 60) a
         left join student b
                   on a.sId = b.id;


# 3、查询在 SC 表存在成绩的学生信息
select s.*
from student s
where s.id in (select distinct sId from sc);


# 4、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(没成绩的显示为 null)
select s.id, s.name, idAndSc.countNum, idAndSc.sums
from student s
         left join (select sc.sId, count(sc.score) countNum, sum(sc.score) sums
                    from sc
                    group by sc.sId) idAndSc on s.id = idAndSc.sId;

# 5、查询「李」姓老师的数量
select count(t.id) counts
from teacher t
where t.name like '李%';

# 6、查询学过「张三」老师授课的同学的信息
select s.*
from student s
         left join sc on s.id = sc.sId
         left join course c on c.id = sc.cId
         left join teacher t on t.id = c.tId
where t.name = '张三';

# 7、查询没有学全所有课程的同学的信息
select s.*, idAndCount.counts
from student s
         left join
     (select sId, count(sId) counts
      from sc
      group by sId
      having counts < (select count(1) from course)) idAndCount
     on s.id = idAndCount.sId;

# group by 报错，为什么
select s.*
from student s
         left join sc on sc.sId = s.id
group by s.id
having count(sc.cId) < (select count(c.id) from course c);

# 8、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
select distinct s.*
from student s
         left join sc on s.id = sc.sId
where sc.cId in (select sc.cId from sc where sId = '01')
  and s.id != '01';

#用union有索引
select distinct s.*
from student s
         left join sc on s.id = sc.sId
where sc.cId in (select sc.cId from sc where sId = '01')
  and s.id > '01'
union
select distinct s.*
from student s
         left join sc on s.id = sc.sId
where sc.cId in (select sc.cId from sc where sId = '01')
  and s.id < '01';


# 9、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
select *
from student
where id in
      (select sId
       from (select *
             from sc a
             where cId in (select sc.cId
                                  # 查学生01的课程cId集合
                           from sc
                           where sc.sId = '01')) b
       group by sId
       having count(cId) = (select count(cId)
                            from sc c
                            where sId = 01))
  and id != '01';

# 10.查询没学过"张三"老师讲授的任一门课程的学生姓名
# 应该少用多个in嵌套
select s.name
from student s
where s.id in (select distinct sc.sId
               from sc
               where sc.cId not in (select c.id
                                    from course c
                                    where c.name = '张三'));

select s.name
from student s
where id not in (select sId
                 from sc
                          left join course on sc.cId = course.id
                          left join teacher t on course.tId = t.id
                 where t.name = '张三');

# 11、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
# only_full_group_by怎么办
select sc.sId, s.name, avg(sc.score) avg
from sc
         left join student s on sc.sId = s.id
where sc.score < 60
group by sc.sId, s.name
having count(1) >= 2;


# 12、检索" 01 "课程分数小于 60，按分数降序排列的学生信息
select s.*
from student s
where s.id in (select sId from sc where cId = '01' and score < 60 order by score);

select s.*, sc.score
from student s
         join sc on s.id = sc.sId
where sc.cId = '01'
  and sc.score < 60
order by sc.score desc;

# 13、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


# 14、查询各科成绩最高分、最低分和平均分
# select c.*, max(sc.score) max, min(sc.score) min, avg(sc.score) avg from course c left join  sc on c.id = sc.cId group by sc.cId;
# select sc.cId, max(sc.score) max, min(sc.score) min, avg(sc.score) avg
# from sc
#          left join course c on c.id = sc.cId
# group by sc.cId;

select cId,
       count(sId)                     count,
       max(score)                     max,
       min(score)                     min,
       avg(score)                     avg,
       sum(pass) / count(sId)      as passRate,
       sum(midum) / count(sId)     as midumRate,
       sum(excellent) / count(sId) as excellentRate,
       sum(good) / count(sId)      as goodRate
from (select *,
             IF(score >= 60, 1, 0)                as pass,
             IF(score >= 70 and score < 80, 1, 0) as midum,
             IF(score >= 80 and score < 90, 1, 0) as excellent,
             IF(score >= 90, 1, 0)                as good
      from sc) a
group by cId
order by count(sId) desc, cId;

# 15.1 按各科成绩进行行排序，并显示排名， Score 重复时合并名次

# select a.*,count(b.score)+1  from sc a
#     left join sc b on a.cid = b.cid and a.score < b.score
# group by a.cid,a.sid
# order by a.cid;


# 16、查询学生的总成绩，并进行排名，总分重复时保留名次空缺
# todo 不会做排名,一般建议在Java代码里做
select s.id, s.name, sum(sc.score) total
from sc
         left join student s on s.id = sc.sId
group by s.id, s.name
order by total;

# 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]，[60-0] 及所占百分比

# 18、查询各科成绩前三名的记录

# 19、查询每门课程被选修的学生数
select count(1) count, c.name
from sc
         left join course c on c.id = sc.cId
group by c.name;


# 20、查询出只选修两门课程的学生学号和姓名
select s.*
from student s
where s.id in (select sc.sId from sc group by sc.sId having count(cId) = 2);

select sc.sId, s.name
from student s
         left join sc on s.id = sc.sId
group by sc.sId, s.name
having count(cId) = 2;


# 21、查询男生、女生人数
select s.sex, count(s.id) count
from student s
group by s.sex;

# 22、查询名字中含有「风」字的学生信息
select s.*
from student s
where s.name like '%风%';

# 23、查询同名同性学生名单，并统计同名人数
# select s.*,s1.*,count(s.id) from student s inner join student s1 on s1.name = s.name

# 24、查询 1990 年出生的学生名单
select s.*
from student s
where s.age between '1990-01-01' and '1990-12-31';
#如果有索引的话下面对age进行计算不会走索引
select s.*
from student s
where year(s.age) = 1990;

# 25、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 sc.cId, c.name, avg(sc.score) avg
from sc
         left join course c on c.id = sc.cId
group by sc.cId, c.name
order by avg desc;


#26、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
select s.id, s.name, avg(sc.score) avg
from sc
         left join student s on s.id = sc.sId
group by s.id, s.name
having avg >= 85;

# 27、查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
select s.name, sc.score
from sc
         left join student s on s.id = sc.sId
where sc.score < 60;

# 28、查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

# 29、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
select s.name studentName, c.name courseName, sc.score
from sc
         left join student s on s.id = sc.sId
         left join course c on c.id = sc.cId
where sc.score > 70;

# 30、查询不及格的课程

# 31、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
select s.id, s.name, sc.score
from sc
         left join student s on s.id = sc.sId
where sc.cId = '01'
  and sc.score >= 80;

# 32、求每门课程的学生人数
select sc.cId, c.name, count(sc.sId) count
from sc
         left join course c on c.id = sc.cId
group by sc.cId, c.name;

#33、成绩不重复，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
select s.*, sc.score
from sc
         left join student s on s.id = sc.sId
where sc.cId = (select c.id
                from course c
                         left join teacher t on c.tId = t.id
                where t.name = '张三'
                limit 1)
order by sc.score desc
limit 1;

# 34、成绩有重复的情况下，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
# TODO,有点麻烦等会做
# 使用max找重复情况下成绩最高的
select sc.score maxScore, s.*
from sc
         left join student s on s.id = sc.sId
where sc.score = (select max(sc.score) from sc)
  and sc.cId = (select c.id
                from course c
                         left join teacher t on c.tId = t.id
                where t.name = '张三'
                limit 1)
order by sc.score desc;

# 35、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


#36、查询每门功成绩最好的前两名
# which is not functionally dependent on columns in GROUP BY clause
# TODO 到底如何规避此问题
select sc.score
from sc
group by sc.cId, sc.score
limit 2;
#37、统计每门课程的学生选修人数（超过 5 人的课程才统计）
select count(sc.sId) count, c.name
from sc
         left join course c on sc.cId = c.id
group by sc.cId, c.name
having count > 5;

#38、检索至少选修两门课程的学生学号
select sc.sId
from sc
group by sc.sId
having count(sc.cId) >= 2;

#39、查询选修了全部课程的学生信息
select sc.sId, s.name, s.age, s.sex
from sc
         left join student s on sc.sId = s.id
group by sc.sId, s.name, s.age, s.sex
having count(sc.cId) = (select count(1) from course);

#40、查询各学生的年龄，只按年份来算
select s.id, s.name, s.sex, (year(now()) - year(s.age))  age
from student s;
#41、按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一

#42、查询本周过生日的学生
select s.* from student s where week(s.age) = week(now())
#43、查询下周过生日的学生
#44、查询本月过生日的学生
#45、查询下月过生日的学生