50道SQL练习题
数据表介绍
--1.学生表
Student(SId,Sname,Sage,Ssex)
--SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
--2.课程表
Course(CId,Cname,TId)
--CId 课程编号,Cname 课程名称,TId 教师编号
--3.教师表
Teacher(TId,Tname)
--TId 教师编号,Tname 教师姓名
--4.成绩表
SC(SId,CId,score)
--SId 学生编号,CId 课程编号,score 分数
学生表 Student
create table Student(SId varchar(10),Sname varchar(10),Sage datetime,Ssex varchar(10));
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' , '1990-12-20' , '男');
insert into Student values('04' , '李云' , '1990-12-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-01-01' , '女');
insert into Student values('07' , '郑竹' , '1989-01-01' , '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' , '2012-06-06' , '女');
insert into Student values('12' , '赵六' , '2013-06-13' , '女');
insert into Student values('13' , '孙七' , '2014-06-01' , '女');科目表 Course
create table Course(CId varchar(10),Cname nvarchar(10),TId varchar(10));
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 Teacher
create table Teacher(TId varchar(10),Tname varchar(10));
insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');成绩表 SC
create table SC(SId varchar(10),CId varchar(10),score decimal(18,1));
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);练习题目
1.查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数
mysql> SELECT
-> s.*,
-> sc1.score AS score_01,
-> sc2.score AS score_02
-> FROM
-> student s
-> JOIN
-> sc sc1 ON s.SId = sc1.SId AND sc1.CId = '01'
-> JOIN
-> sc sc2 ON s.SId = sc2.SId AND sc2.CId = '02'
-> WHERE
-> sc1.score > sc2.score;
+------+--------+---------------------+------+----------+----------+
| SId | Sname | Sage | Ssex | score_01 | score_02 |
+------+--------+---------------------+------+----------+----------+
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 | 70.0 | 60.0 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 | 50.0 | 30.0 |
+------+--------+---------------------+------+----------+----------+
1.1查询同时存在" 01 "课程和" 02 "课程的情况
mysql> SELECT sc1.SId
-> FROM sc sc1
-> JOIN sc sc2 ON sc1.SId = sc2.SId
-> WHERE sc1.CId = '01' AND sc2.CId = '02';
+------+
| SId |
+------+
| 01 |
| 02 |
| 03 |
| 04 |
| 05 |
+------+
1.2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 )
mysql> SELECT
-> sc1.SId,
-> sc1.CId AS CId_01,
-> sc1.score AS score_01,
-> sc2.CId AS CId_02,
-> sc2.score AS score_02
-> FROM
-> sc sc1
-> LEFT JOIN
-> sc sc2 ON sc1.SId = sc2.SId AND sc2.CId = '02'
-> WHERE
-> sc1.CId = '01';
+------+--------+----------+--------+----------+
| SId | CId_01 | score_01 | CId_02 | score_02 |
+------+--------+----------+--------+----------+
| 01 | 01 | 80.0 | 02 | 90.0 |
| 02 | 01 | 70.0 | 02 | 60.0 |
| 03 | 01 | 80.0 | 02 | 80.0 |
| 04 | 01 | 50.0 | 02 | 30.0 |
| 05 | 01 | 76.0 | 02 | 87.0 |
| 06 | 01 | 31.0 | NULL | NULL |
+------+--------+----------+--------+----------+
1.3查询不存在" 01 "课程但存在" 02 "课程的情况
mysql> SELECT *
-> FROM sc
-> WHERE SId NOT IN (SELECT SId FROM sc WHERE CId = '01')
-> AND CId = '02';
+------+------+-------+
| SId | CId | score |
+------+------+-------+
| 07 | 02 | 89.0 |
+------+------+-------+
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
mysql> SELECT student.SId, student.Sname, AVG(score)
-> FROM sc
-> LEFT JOIN student ON sc.SId = student.SId
-> GROUP BY student.SId, student.Sname
-> HAVING AVG(score) > 60;
+------+--------+------------+
| SId | Sname | AVG(score) |
+------+--------+------------+
| 01 | 赵雷 | 89.66667 |
| 02 | 钱电 | 70.00000 |
| 03 | 孙风 | 80.00000 |
| 05 | 周梅 | 81.50000 |
| 07 | 郑竹 | 93.50000 |
+------+--------+------------+
5 rows in set (0.00 sec)
3.查询在 SC 表存在成绩的学生信息
mysql> select distinct student.*
-> from sc left join student
-> on sc.SId = student.SId;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
7 rows in set (0.00 sec)
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 )
mysql> select student.SId,student.Sname,count(*) as '选课总数',sum(sc.score) as '课程总成绩'
-> from student left join sc on student.SId=sc.SId
-> group by student.SId,student.Sname;
+------+--------+--------------+-----------------+
| SId | Sname | 选课总数 | 课程总成绩 |
+------+--------+--------------+-----------------+
| 01 | 赵雷 | 3 | 269.0 |
| 02 | 钱电 | 3 | 210.0 |
| 03 | 孙风 | 3 | 240.0 |
| 04 | 李云 | 3 | 100.0 |
| 05 | 周梅 | 2 | 163.0 |
| 06 | 吴兰 | 2 | 65.0 |
| 07 | 郑竹 | 2 | 187.0 |
| 09 | 张三 | 1 | NULL |
| 10 | 李四 | 1 | NULL |
| 11 | 李四 | 1 | NULL |
| 12 | 赵六 | 1 | NULL |
| 13 | 孙七 | 1 | NULL |
+------+--------+--------------+-----------------+
12 rows in set (0.00 sec)
4.1 查有成绩的学生信息
mysql> select distinct student.*
-> from sc left join student
-> on sc.SId = student.SId;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
7 rows in set (0.00 sec)
5.查询「李」姓老师的数量
mysql> SELECT COUNT(*)
-> FROM teacher
-> WHERE Tname LIKE '李%';
+----------+
| COUNT(*) |
+----------+
| 1 |
+----------+
1 row in set (0.01 sec)
6.查询学过「张三」老师授课的同学的信息
mysql> SELECT s.*
-> FROM Student s
-> JOIN SC sc ON s.SId = sc.SId
-> JOIN Course c ON sc.CId = c.CId
-> JOIN Teacher t ON c.TId = t.TId
-> WHERE t.Tname = '张三';
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
6 rows in set (0.03 sec)
7.查询没有学全所有课程的同学的信息
mysql> SELECT s.*
-> FROM student s
-> JOIN (
-> SELECT SId, COUNT(*) AS c
-> FROM sc
-> GROUP BY SId
-> ) sc ON s.SId = sc.SId
-> WHERE sc.c < (SELECT COUNT(*) FROM course);
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
3 rows in set (0.01 sec)
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
mysql> SELECT s.*
-> FROM Student s
-> WHERE s.SId IN (
-> SELECT DISTINCT sc.SId
-> FROM SC sc
-> WHERE sc.CId IN (
-> SELECT CId
-> FROM SC
-> WHERE SId = '01'
-> ) AND sc.SId != '01'
-> );
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 05 | 周梅 | 1991-12-01 00:00:00 | 女 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
| 07 | 郑竹 | 1989-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
6 rows in set (0.00 sec)
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
mysql> WITH student_01_courses AS (
-> SELECT CId
-> FROM sc
-> WHERE SId = '01'
-> ),
-> -- 统计 01 号同学所选课程的数量
-> student_01_course_count AS (
-> SELECT COUNT(*) AS course_count
-> FROM student_01_courses
-> )
-> -- 主查询，找出符合条件的其他同学信息
-> SELECT s.*
-> FROM student s
-> JOIN (
-> -- 子查询：统计每个学生的选课数量
-> SELECT SId, COUNT(CId) AS course_count
-> FROM sc
-> GROUP BY SId
-> ) student_course_counts ON s.SId = student_course_counts.SId
-> JOIN student_01_course_count s01cc ON student_course_counts.course_count = s01cc.course_count
-> WHERE s.SId != '01'
-> AND NOT EXISTS (
-> -- 检查是否有 01 号同学选的课，当前学生没选
-> SELECT 1
-> FROM student_01_courses
-> WHERE CId NOT IN (
-> SELECT CId
-> FROM sc
-> WHERE SId = s.SId
-> )
-> );
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
+------+--------+---------------------+------+
3 rows in set (0.00 sec)
10.查询没学过"张三"老师讲授的任一门课程的学生姓名
mysql> WITH zhangsan_courses AS (
-> SELECT c.CId
-> FROM course c
-> JOIN teacher t ON c.TId = t.TId
-> WHERE t.TName = '张三'
-> )
-> SELECT s.SName
-> FROM student s
-> WHERE s.SId NOT IN (
-> SELECT DISTINCT sc.SId
-> FROM sc
-> JOIN zhangsan_courses zc ON sc.CId = zc.CId
-> );
+--------+
| SName |
+--------+
| 吴兰 |
| 张三 |
| 李四 |
| 李四 |
| 赵六 |
| 孙七 |
+--------+
6 rows in set (0.02 sec)
mysql>
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
mysql> WITH student_failure_stats AS (
-> SELECT
-> s.SId,
-> s.SName,
-> COUNT(CASE WHEN sc.Score < 60 THEN 1 END) AS failure_count,
-> AVG(sc.Score) AS average_score
-> FROM
-> student s
-> JOIN
-> sc ON s.SId = sc.SId
-> GROUP BY
-> s.SId, s.SName
-> )
-> SELECT
-> SId,
-> SName,
-> average_score
-> FROM
-> student_failure_stats
-> WHERE
-> failure_count >= 2;
+------+--------+---------------+
| SId | SName | average_score |
+------+--------+---------------+
| 04 | 李云 | 33.33333 |
| 06 | 吴兰 | 32.50000 |
+------+--------+---------------+
2 rows in set (0.00 sec)
12.检索" 01 "课程分数小于 60，按分数降序排列的学生信息
mysql> SELECT s.*
-> FROM student s
-> JOIN sc ON s.SId = sc.SId
-> WHERE sc.CId = '01' AND sc.Score < 60
-> ORDER BY sc.Score DESC;
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
| 06 | 吴兰 | 1992-01-01 00:00:00 | 女 |
+------+--------+---------------------+------+
2 rows in set (0.00 sec)
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
mysql> WITH student_avg_score AS (
-> SELECT
-> SId,
-> AVG(Score) AS avg_score
-> FROM
-> sc
-> GROUP BY
-> SId
-> )
-> SELECT
-> s.SId,
-> s.SName,
-> sc.CId,
-> sc.Score,
-> sas.avg_score
-> FROM
-> student s
-> JOIN
-> sc ON s.SId = sc.SId
-> JOIN
-> student_avg_score sas ON s.SId = sas.SId
-> ORDER BY
-> sas.avg_score DESC;
+------+--------+------+-------+-----------+
| SId | SName | CId | Score | avg_score |
+------+--------+------+-------+-----------+
| 07 | 郑竹 | 02 | 89.0 | 93.50000 |
| 07 | 郑竹 | 03 | 98.0 | 93.50000 |
| 01 | 赵雷 | 01 | 80.0 | 89.66667 |
| 01 | 赵雷 | 02 | 90.0 | 89.66667 |
| 01 | 赵雷 | 03 | 99.0 | 89.66667 |
| 05 | 周梅 | 01 | 76.0 | 81.50000 |
| 05 | 周梅 | 02 | 87.0 | 81.50000 |
| 03 | 孙风 | 01 | 80.0 | 80.00000 |
| 03 | 孙风 | 02 | 80.0 | 80.00000 |
| 03 | 孙风 | 03 | 80.0 | 80.00000 |
| 02 | 钱电 | 01 | 70.0 | 70.00000 |
| 02 | 钱电 | 02 | 60.0 | 70.00000 |
| 02 | 钱电 | 03 | 80.0 | 70.00000 |
| 04 | 李云 | 01 | 50.0 | 33.33333 |
| 04 | 李云 | 02 | 30.0 | 33.33333 |
| 04 | 李云 | 03 | 20.0 | 33.33333 |
| 06 | 吴兰 | 01 | 31.0 | 32.50000 |
| 06 | 吴兰 | 03 | 34.0 | 32.50000 |
+------+--------+------+-------+-----------+
18 rows in set (0.00 sec)
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
mysql>
mysql> WITH course_stats AS (
-> SELECT
-> c.CId,
-> c.CName,
-> COUNT(sc.SId) AS student_count,
-> MAX(sc.Score) AS max_score,
-> MIN(sc.Score) AS min_score,
-> AVG(sc.Score) AS avg_score,
-> SUM(CASE WHEN sc.Score >= 60 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS pass_rate,
-> SUM(CASE WHEN sc.Score BETWEEN 70 AND 80 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS medium_rate,
-> SUM(CASE WHEN sc.Score BETWEEN 80 AND 90 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS good_rate,
-> SUM(CASE WHEN sc.Score >= 90 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS excellent_rate
-> FROM
-> course c
-> LEFT JOIN
-> sc ON c.CId = sc.CId
-> GROUP BY
-> c.CId, c.CName
-> )
-> SELECT
-> CId,
-> CName,
-> max_score,
-> min_score,
-> avg_score,
-> pass_rate,
-> medium_rate,
-> good_rate,
-> excellent_rate,
-> student_count
-> FROM
-> course_stats
-> ORDER BY
-> student_count DESC,
-> CId ASC;
+------+--------+-----------+-----------+-----------+-----------+-------------+-----------+----------------+---------------+
| CId | CName | max_score | min_score | avg_score | pass_rate | medium_rate | good_rate | excellent_rate | student_count |
+------+--------+-----------+-----------+-----------+-----------+-------------+-----------+----------------+---------------+
| 01 | 语文 | 80.0 | 31.0 | 64.50000 | 0.6667 | 0.6667 | 0.3333 | 0.0000 | 6 |
| 02 | 数学 | 90.0 | 30.0 | 72.66667 | 0.8333 | 0.1667 | 0.6667 | 0.1667 | 6 |
| 03 | 英语 | 99.0 | 20.0 | 68.50000 | 0.6667 | 0.3333 | 0.3333 | 0.3333 | 6 |
+------+--------+-----------+-----------+-----------+-----------+-------------+-----------+----------------+---------------+
3 rows in set (0.01 sec)
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
mysql> SELECT
-> SId,
-> CId,
-> Score,
-> RANK() OVER (PARTITION BY CId ORDER BY Score DESC) AS ranking
-> FROM
-> sc
-> ORDER BY
-> CId,
-> ranking;
+------+------+-------+---------+
| SId | CId | Score | ranking |
+------+------+-------+---------+
| 01 | 01 | 80.0 | 1 |
| 03 | 01 | 80.0 | 1 |
| 05 | 01 | 76.0 | 3 |
| 02 | 01 | 70.0 | 4 |
| 04 | 01 | 50.0 | 5 |
| 06 | 01 | 31.0 | 6 |
| 01 | 02 | 90.0 | 1 |
| 07 | 02 | 89.0 | 2 |
| 05 | 02 | 87.0 | 3 |
| 03 | 02 | 80.0 | 4 |
| 02 | 02 | 60.0 | 5 |
| 04 | 02 | 30.0 | 6 |
| 01 | 03 | 99.0 | 1 |
| 07 | 03 | 98.0 | 2 |
| 02 | 03 | 80.0 | 3 |
| 03 | 03 | 80.0 | 3 |
| 06 | 03 | 34.0 | 5 |
| 04 | 03 | 20.0 | 6 |
+------+------+-------+---------+
18 rows in set (0.01 sec)
mysql>
15.1 按各科成绩进行排序，并显示排名， Score 重复时合并名次
mysql> SELECT
-> SId,
-> CId,
-> Score,
-> DENSE_RANK() OVER (PARTITION BY CId ORDER BY Score DESC) AS ranking
-> FROM
-> sc
-> ORDER BY
-> CId,
-> ranking;
+------+------+-------+---------+
| SId | CId | Score | ranking |
+------+------+-------+---------+
| 01 | 01 | 80.0 | 1 |
| 03 | 01 | 80.0 | 1 |
| 05 | 01 | 76.0 | 2 |
| 02 | 01 | 70.0 | 3 |
| 04 | 01 | 50.0 | 4 |
| 06 | 01 | 31.0 | 5 |
| 01 | 02 | 90.0 | 1 |
| 07 | 02 | 89.0 | 2 |
| 05 | 02 | 87.0 | 3 |
| 03 | 02 | 80.0 | 4 |
| 02 | 02 | 60.0 | 5 |
| 04 | 02 | 30.0 | 6 |
| 01 | 03 | 99.0 | 1 |
| 07 | 03 | 98.0 | 2 |
| 02 | 03 | 80.0 | 3 |
| 03 | 03 | 80.0 | 3 |
| 06 | 03 | 34.0 | 4 |
| 04 | 03 | 20.0 | 5 |
+------+------+-------+---------+
18 rows in set (0.00 sec)
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
mysql> SELECT
-> SId,
-> SUM(Score) AS total_score,
-> RANK() OVER (ORDER BY SUM(Score) DESC) AS ranking
-> FROM
-> sc
-> GROUP BY
-> SId
-> ORDER BY
-> ranking;
+------+-------------+---------+
| SId | total_score | ranking |
+------+-------------+---------+
| 01 | 269.0 | 1 |
| 03 | 240.0 | 2 |
| 02 | 210.0 | 3 |
| 07 | 187.0 | 4 |
| 05 | 163.0 | 5 |
| 04 | 100.0 | 6 |
| 06 | 65.0 | 7 |
+------+-------------+---------+
7 rows in set (0.00 sec)
16.1 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
mysql> SELECT
-> SId,
-> SUM(Score) AS total_score,
-> DENSE_RANK() OVER (ORDER BY SUM(Score) DESC) AS ranking
-> FROM
-> sc
-> GROUP BY
-> SId
-> ORDER BY
-> ranking;
+------+-------------+---------+
| SId | total_score | ranking |
+------+-------------+---------+
| 01 | 269.0 | 1 |
| 03 | 240.0 | 2 |
| 02 | 210.0 | 3 |
| 07 | 187.0 | 4 |
| 05 | 163.0 | 5 |
| 04 | 100.0 | 6 |
| 06 | 65.0 | 7 |
+------+-------------+---------+
7 rows in set (0.00 sec)
mysql>
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
mysql> SELECT
-> c.CId,
-> c.CName,
-> SUM(CASE WHEN sc.Score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) AS score_85_100,
-> SUM(CASE WHEN sc.Score BETWEEN 85 AND 100 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS percentage_85_100,
-> SUM(CASE WHEN sc.Score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) AS score_70_85,
-> SUM(CASE WHEN sc.Score BETWEEN 70 AND 85 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS percentage_70_85,
-> SUM(CASE WHEN sc.Score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) AS score_60_70,
-> SUM(CASE WHEN sc.Score BETWEEN 60 AND 70 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS percentage_60_70,
-> SUM(CASE WHEN sc.Score BETWEEN 0 AND 60 THEN 1 ELSE 0 END) AS score_0_60,
-> SUM(CASE WHEN sc.Score BETWEEN 0 AND 60 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS percentage_0_60
-> FROM
-> course c
-> LEFT JOIN
-> sc ON c.CId = sc.CId
-> GROUP BY
-> c.CId, c.CName
-> ORDER BY
-> c.CId;
+------+--------+--------------+-------------------+-------------+------------------+-------------+------------------+------------+-----------------+
| CId | CName | score_85_100 | percentage_85_100 | score_70_85 | percentage_70_85 | score_60_70 | percentage_60_70 | score_0_60 | percentage_0_60 |
+------+--------+--------------+-------------------+-------------+------------------+-------------+------------------+------------+-----------------+
| 01 | 语文 | 0 | 0.0000 | 4 | 0.6667 | 1 | 0.1667 | 2 | 0.3333 |
| 02 | 数学 | 3 | 0.5000 | 1 | 0.1667 | 1 | 0.1667 | 2 | 0.3333 |
| 03 | 英语 | 2 | 0.3333 | 2 | 0.3333 | 0 | 0.0000 | 2 | 0.3333 |
+------+--------+--------------+-------------------+-------------+------------------+-------------+------------------+------------+-----------------+
3 rows in set (0.00 sec)
18.查询各科成绩前三名的记录
mysql> WITH ranked_scores AS (
-> SELECT
-> SId,
-> CId,
-> Score,
-> RANK() OVER (PARTITION BY CId ORDER BY Score DESC) AS ranking
-> FROM
-> sc
-> )
-> SELECT
-> SId,
-> CId,
-> Score
-> FROM
-> ranked_scores
-> WHERE
-> ranking <= 3
-> ORDER BY
-> CId,
-> ranking;
+------+------+-------+
| SId | CId | Score |
+------+------+-------+
| 01 | 01 | 80.0 |
| 03 | 01 | 80.0 |
| 05 | 01 | 76.0 |
| 01 | 02 | 90.0 |
| 07 | 02 | 89.0 |
| 05 | 02 | 87.0 |
| 01 | 03 | 99.0 |
| 07 | 03 | 98.0 |
| 02 | 03 | 80.0 |
| 03 | 03 | 80.0 |
+------+------+-------+
10 rows in set (0.00 sec)
19.查询每门课程被选修的学生数
mysql> select sc.CId , count(*) as '学生数'
-> from sc
-> group by CId;
+------+-----------+
| CId | 学生数 |
+------+-----------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+-----------+
3 rows in set (0.00 sec)
20.查询出只选修两门课程的学生学号和姓名
mysql> SELECT s.Sname, s.SId
-> FROM student s
-> JOIN (
-> -- 子查询：筛选出选课数量为 2 的学生编号
-> SELECT SId
-> FROM sc
-> GROUP BY SId
-> HAVING COUNT(*) = 2
-> ) selected_students ON s.SId = selected_students.SId;
+--------+------+
| Sname | SId |
+--------+------+
| 周梅 | 05 |
| 吴兰 | 06 |
| 郑竹 | 07 |
+--------+------+
3 rows in set (0.00 sec)
21.查询男生、女生人数
mysql> select count(*) as `人数`,Ssex
-> from student
-> group by Ssex;
+--------+------+
| 人数 | Ssex |
+--------+------+
| 4 | 男 |
| 8 | 女 |
+--------+------+
2 rows in set (0.00 sec)
22.查询名字中含有「风」字的学生信息
mysql> select * from student
-> where Sname like "%风%";
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
+------+--------+---------------------+------+
1 row in set (0.00 sec)
mysql>
23.查询同名同性学生名单，并统计同名人数
mysql> SELECT
-> SName,
-> Ssex,
-> COUNT(*) AS same_name_count
-> FROM
-> student
-> GROUP BY
-> SName, Ssex
-> HAVING
-> COUNT(*) > 1
-> ORDER BY
-> SName, Ssex;
+--------+------+-----------------+
| SName | Ssex | same_name_count |
+--------+------+-----------------+
| 李四 | 女 | 2 |
+--------+------+-----------------+
1 row in set (0.00 sec)
24.查询 1990 年出生的学生名单
mysql> select * from student
-> where Sage like "1990-%";
+------+--------+---------------------+------+
| SId | Sname | Sage | Ssex |
+------+--------+---------------------+------+
| 01 | 赵雷 | 1990-01-01 00:00:00 | 男 |
| 02 | 钱电 | 1990-12-21 00:00:00 | 男 |
| 03 | 孙风 | 1990-12-20 00:00:00 | 男 |
| 04 | 李云 | 1990-12-06 00:00:00 | 男 |
+------+--------+---------------------+------+
4 rows in set (0.00 sec)
mysql>
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
mysql> SELECT
-> CId,
-> AVG(Score) AS avg_score
-> FROM
-> sc
-> GROUP BY
-> CId
-> ORDER BY
-> avg_score DESC,
-> CId ASC;
+------+-----------+
| CId | avg_score |
+------+-----------+
| 02 | 72.66667 |
| 03 | 68.50000 |
| 01 | 64.50000 |
+------+-----------+
3 rows in set (0.00 sec)
mysql>
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
mysql> select s.SId,s.Sname,sc.student_avg
-> from student s
-> join (select SId,avg(score) as student_avg
-> from sc group by SId
-> having avg(score)>=85) sc on s.SId=sc.SId;
+------+--------+-------------+
| SId | Sname | student_avg |
+------+--------+-------------+
| 01 | 赵雷 | 89.66667 |
| 07 | 郑竹 | 93.50000 |
+------+--------+-------------+
2 rows in set (0.00 sec)
27.查询课程名称为「数学」，且分数低于 60 的学生姓名和分数
mysql> select s.Sname,sc.score
-> from student s
-> join sc on s.SId=sc.SId
-> join course on sc.CId=course.CId
-> where course.Cname="数学" and sc.score<60;
+--------+-------+
| Sname | score |
+--------+-------+
| 李云 | 30.0 |
+--------+-------+
1 row in set (0.00 sec)
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）
mysql> SELECT
-> s.SId,
-> s.SName,
-> sc.CId,
-> sc.Score
-> FROM
-> student s
-> LEFT JOIN
-> sc ON s.SId = sc.SId
-> ORDER BY
-> s.SId;
+------+--------+------+-------+
| SId | SName | CId | Score |
+------+--------+------+-------+
| 01 | 赵雷 | 03 | 99.0 |
| 01 | 赵雷 | 02 | 90.0 |
| 01 | 赵雷 | 01 | 80.0 |
| 02 | 钱电 | 03 | 80.0 |
| 02 | 钱电 | 02 | 60.0 |
| 02 | 钱电 | 01 | 70.0 |
| 03 | 孙风 | 03 | 80.0 |
| 03 | 孙风 | 02 | 80.0 |
| 03 | 孙风 | 01 | 80.0 |
| 04 | 李云 | 03 | 20.0 |
| 04 | 李云 | 02 | 30.0 |
| 04 | 李云 | 01 | 50.0 |
| 05 | 周梅 | 02 | 87.0 |
| 05 | 周梅 | 01 | 76.0 |
| 06 | 吴兰 | 03 | 34.0 |
| 06 | 吴兰 | 01 | 31.0 |
| 07 | 郑竹 | 03 | 98.0 |
| 07 | 郑竹 | 02 | 89.0 |
| 09 | 张三 | NULL | NULL |
| 10 | 李四 | NULL | NULL |
| 11 | 李四 | NULL | NULL |
| 12 | 赵六 | NULL | NULL |
| 13 | 孙七 | NULL | NULL |
+------+--------+------+-------+
23 rows in set (0.00 sec)
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
mysql> select s.Sname,c.Cname,sc.Score
-> from student s
-> join sc on s.SId=sc.SId
-> join course c on c.CId=sc.CId
-> where sc.Score >70;
+--------+--------+-------+
| Sname | Cname | Score |
+--------+--------+-------+
| 赵雷 | 英语 | 99.0 |
| 赵雷 | 数学 | 90.0 |
| 赵雷 | 语文 | 80.0 |
| 钱电 | 英语 | 80.0 |
| 孙风 | 英语 | 80.0 |
| 孙风 | 数学 | 80.0 |
| 孙风 | 语文 | 80.0 |
| 周梅 | 数学 | 87.0 |
| 周梅 | 语文 | 76.0 |
| 郑竹 | 英语 | 98.0 |
| 郑竹 | 数学 | 89.0 |
+--------+--------+-------+
11 rows in set (0.00 sec)
30.查询不及格的课程
mysql> select s.Sname,c.Cname,sc.Score
-> from student s
-> join sc on s.SId=sc.SId
-> join course c on c.CId=sc.CId
-> where sc.Score <60;
+--------+--------+-------+
| Sname | Cname | Score |
+--------+--------+-------+
| 李云 | 英语 | 20.0 |
| 李云 | 数学 | 30.0 |
| 李云 | 语文 | 50.0 |
| 吴兰 | 英语 | 34.0 |
| 吴兰 | 语文 | 31.0 |
+--------+--------+-------+
5 rows in set (0.00 sec)
mysql>
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
mysql> select s.Sname,c.Cname,sc.Score
-> from student s
-> join sc on s.SId=sc.SId
-> join course c on c.CId=sc.CId
-> where sc.Score >=80 and c.CId= '01';
+--------+--------+-------+
| Sname | Cname | Score |
+--------+--------+-------+
| 赵雷 | 语文 | 80.0 |
| 孙风 | 语文 | 80.0 |
+--------+--------+-------+
2 rows in set (0.00 sec)
mysql>
32.求每门课程的学生人数
mysql> select CId,count(*) as `人数`
-> from sc
-> group by CId;
+------+--------+
| CId | 人数 |
+------+--------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+--------+
3 rows in set (0.00 sec)
mysql>
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
mysql> WITH zhangsan_courses AS (
-> SELECT c.CId
-> FROM course c
-> JOIN teacher t ON c.TId = t.TId
-> WHERE t.TName = '张三'
-> ),
-> -- 接着找出选修张三老师课程的学生成绩，并按成绩降序排列
-> student_scores AS (
-> SELECT s.SId, s.SName, sc.Score
-> FROM student s
-> JOIN sc ON s.SId = sc.SId
-> JOIN zhangsan_courses zc ON sc.CId = zc.CId
-> ORDER BY sc.Score DESC
-> )
-> -- 最后取排序后的第一条记录，即成绩最高的学生信息
-> SELECT *
-> FROM student_scores
-> LIMIT 1; +
+------+--------+-------+
| SId | SName | Score |
+------+--------+-------+
| 01 | 赵雷 | 90.0 |
+------+--------+-------+
1 row in set (0.00 sec)
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
mysql> WITH zhangsan_courses AS (
-> SELECT c.CId
-> FROM course c
-> JOIN teacher t ON c.TId = t.TId
-> WHERE t.TName = '张三'
-> ),
-> -- 找出选修张三老师课程的学生成绩，并计算排名
-> student_scores_ranked AS (
-> SELECT
-> s.SId,
-> s.SName,
-> sc.Score,
-> RANK() OVER (ORDER BY sc.Score DESC) AS ranking
-> FROM
-> student s
-> JOIN
-> sc ON s.SId = sc.SId
-> JOIN
-> zhangsan_courses zc ON sc.CId = zc.CId
-> )
-> -- 筛选出排名为 1 的学生信息
-> SELECT
-> SId,
-> SName,
-> Score
-> FROM
-> student_scores_ranked
-> WHERE
-> ranking = 1;
+------+--------+-------+
| SId | SName | Score |
+------+--------+-------+
| 01 | 赵雷 | 90.0 |
+------+--------+-------+
1 row in set (0.00 sec)
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
mysql> SELECT
-> s1.SId,
-> s1.CId,
-> s1.Score
-> FROM
-> sc s1
-> JOIN
-> sc s2
-> ON
-> s1.SId = s2.SId
-> AND s1.CId != s2.CId
-> AND s1.Score = s2.Score
-> GROUP BY
-> s1.SId, s1.CId, s1.Score
-> ORDER BY
-> s1.SId, s1.CId;
+------+------+-------+
| SId | CId | Score |
+------+------+-------+
| 03 | 01 | 80.0 |
| 03 | 02 | 80.0 |
| 03 | 03 | 80.0 |
+------+------+-------+
3 rows in set (0.01 sec)
36.查询每门功成绩最好的前两名
mysql> SELECT
-> s1.SId,
-> s1.CId,
-> s1.Score
-> FROM
-> sc s1
-> WHERE
-> (
-> -- 子查询，统计成绩比当前记录高的数量
-> SELECT
-> COUNT(*)
-> FROM
-> sc s2
-> WHERE
-> s1.CId = s2.CId
-> AND s2.Score > s1.Score
-> ) < 2
-> ORDER BY
-> s1.CId,
-> s1.Score DESC;
+------+------+-------+
| SId | CId | Score |
+------+------+-------+
| 01 | 01 | 80.0 |
| 03 | 01 | 80.0 |
| 01 | 02 | 90.0 |
| 07 | 02 | 89.0 |
| 01 | 03 | 99.0 |
| 07 | 03 | 98.0 |
+------+------+-------+
6 rows in set (0.00 sec)
37.统计每门课程的学生选修人数（超过 5 人的课程才统计）。
mysql> SELECT
-> CId,
-> COUNT(SId) AS enrollment_count
-> FROM
-> sc
-> GROUP BY
-> CId
-> HAVING
-> COUNT(SId) > 5
-> ORDER BY
-> CId;
+------+------------------+
| CId | enrollment_count |
+------+------------------+
| 01 | 6 |
| 02 | 6 |
| 03 | 6 |
+------+------------------+
3 rows in set (0.00 sec)
mysql>
38.检索至少选修两门课程的学生学号
mysql> select SId
-> from sc
-> group by SId
-> having count(*) >=2;
+------+
| SId |
+------+
| 01 |
| 02 |
| 03 |
| 04 |
| 05 |
| 06 |
| 07 |
+------+
7 rows in set (0.00 sec)
mysql>
39.查询选修了全部课程的学生信息
mysql> WITH total_course_count AS (
-> SELECT COUNT(CId) AS total_courses
-> FROM course
-> ),
-> -- 子查询统计每个学生选修的课程数
-> student_course_count AS (
-> SELECT
-> SId,
-> COUNT(CId) AS course_count
-> FROM
-> sc
-> GROUP BY
-> SId
-> )
-> -- 主查询获取选修了全部课程的学生信息
-> SELECT
-> s.SId,
-> s.SName
-> FROM
-> student s
-> JOIN
-> student_course_count scc ON s.SId = scc.SId
-> JOIN
-> total_course_count tcc ON 1 = 1
-> WHERE
-> scc.course_count = tcc.total_courses;
+------+--------+
| SId | SName |
+------+--------+
| 01 | 赵雷 |
| 02 | 钱电 |
| 03 | 孙风 |
| 04 | 李云 |
+------+--------+
4 rows in set (0.00 sec)
40.查询各学生的年龄，只按年份来算
mysql> SELECT
-> SId,
-> SName,
-> -- 使用 YEAR 函数获取当前年份减去出生年份来计算年龄
-> YEAR(CURDATE()) - YEAR(Sage) AS age
-> FROM
-> student;
+------+--------+------+
| SId | SName | age |
+------+--------+------+
| 01 | 赵雷 | 35 |
| 02 | 钱电 | 35 |
| 03 | 孙风 | 35 |
| 04 | 李云 | 35 |
| 05 | 周梅 | 34 |
| 06 | 吴兰 | 33 |
| 07 | 郑竹 | 36 |
| 09 | 张三 | 8 |
| 10 | 李四 | 8 |
| 11 | 李四 | 13 |
| 12 | 赵六 | 12 |
| 13 | 孙七 | 11 |
+------+--------+------+
12 rows in set (0.00 sec)
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
mysql> SELECT
-> SId,
-> SName,
-> -- 使用 CASE 语句根据条件计算年龄
-> CASE
-> WHEN MONTH(CURDATE()) < MONTH(Sage) OR (MONTH(CURDATE()) = MONTH(Sage) AND DAY(CURDATE()) < DAY(Sage))
-> THEN YEAR(CURDATE()) - YEAR(Sage) - 1
-> ELSE YEAR(CURDATE()) - YEAR(Sage)
-> END AS age
-> FROM
-> student;
+------+--------+------+
| SId | SName | age |
+------+--------+------+
| 01 | 赵雷 | 35 |
| 02 | 钱电 | 34 |
| 03 | 孙风 | 34 |
| 04 | 李云 | 34 |
| 05 | 周梅 | 33 |
| 06 | 吴兰 | 33 |
| 07 | 郑竹 | 36 |
| 09 | 张三 | 7 |
| 10 | 李四 | 7 |
| 11 | 李四 | 12 |
| 12 | 赵六 | 11 |
| 13 | 孙七 | 10 |
+------+--------+------+
12 rows in set (0.00 sec)
42.查询本周过生日的学生
SELECT
SId,
SName,
Sage
FROM
student
WHERE
-- 使用 WEEK 和 YEAR 函数获取下周的年份和周数，与学生生日的年份和周数进行比较
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = WEEK(Sage) AND YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = YEAR(Sage)) OR
-- 处理跨年的情况，生日在下周但年份不同
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 1 AND WEEK(Sage) = 52 AND YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) - YEAR(Sage) = 1) OR
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 52 AND WEEK(Sage) = 1 AND YEAR(Sage) - YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 1);
43.查询下周过生日的学生
SELECT
SId,
SName,
Sage
FROM
student
WHERE
-- 使用 WEEK 和 YEAR 函数获取下周的年份和周数，与学生生日的年份和周数进行比较
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = WEEK(Sage) AND YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = YEAR(Sage)) OR
-- 处理跨年的情况，生日在下周但年份不同
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 1 AND WEEK(Sage) = 52 AND YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) - YEAR(Sage) = 1) OR
(WEEK(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 52 AND WEEK(Sage) = 1 AND YEAR(Sage) - YEAR(DATE_ADD(CURDATE(), INTERVAL 1 WEEK)) = 1);
44.查询本月过生日的学生
mysql> SELECT
-> SId,
-> SName,
-> Sage
-> FROM
-> student
-> WHERE
-> -- 使用 MONTH 函数获取当前月和学生生日的月进行比较
-> MONTH(CURDATE()) = MONTH(Sage);
Empty set (0.00 sec)
45.查询下月过生日的学生
mysql> SELECT
-> SId,
-> SName,
-> Sage
-> FROM
-> student
-> WHERE
-> -- 使用 MONTH 函数获取下月的月和学生生日的月进行比较
-> MONTH(DATE_ADD(CURDATE(), INTERVAL 1 MONTH)) = MONTH(Sage);
Empty set (0.00 sec)