MYSQL之SQL练习50题

此次针对SQL进行整体练习，将SQL练习50题进行解答。题目的难度各有差异，难度不是按照题目顺序进行的排序。

其中题目有所参考网上答案，对于个别题目的结果差异，可能是个人理解题意的差异不同造成的，答案不一定正确，但记录一下SQL的常用语法操作。

创建数据表，如果同时执行造成创建失败，请删除各个表，进行逐次创建，

为了方便，出生年月日使用的日期类型，分数使用INT(n)，其他字段全部设置为VARCHAR(n)

-- 创建学生表
CREATE TABLE Student(
    StuNum VARCHAR(20), -- 学号
    StuName VARCHAR(20),-- 学生姓名
    StuBirth DATE,    -- 出生年月日
    StuSex VARCHAR(20), -- 性别
    CONSTRAINT PK_Num PRIMARY KEY(StuNum) -- 设置学号为主键
);

-- 创建教师表
CREATE TABLE Teacher(
    TchNum VARCHAR(20), -- 教师编号
    TchName VARCHAR(20), -- 教师名字
    CONSTRAINT PK_Num PRIMARY KEY(TchNum) -- 设置教师编号为主键
);

-- 创建课程表
CREATE TABLE Course(
    CrNum VARCHAR(20), -- 课程编号
    CrName VARCHAR(20), -- 课程名称
    TchNum VARCHAR(20), -- 教师编号
    CONSTRAINT PK_Num PRIMARY KEY(CrNum) -- 设置课程编号为主键
);

-- 创建成绩表
CREATE TABLE Score(
    StuNum VARCHAR(20),-- 学号
    CrNum VARCHAR(20), -- 课程编号
    SrScore INT(3), -- 学科分数
    CONSTRAINT PK_StuCrNum PRIMARY KEY(StuNum,CrNum) -- 设置学号、课程编号为联合主键
);

导入数据，使用插入语句进行数据的导入

-- 插入学生表测试数据
insert into Student values('2019001' , '赵雷' , '1990-01-01' , '男');
insert into Student values('2019002' , '钱电' , '1990-12-21' , '男');
insert into Student values('2019003' , '孙风' , '1990-05-20' , '男');
insert into Student values('2019004' , '李云' , '1990-08-06' , '男');
insert into Student values('2019005' , '周梅' , '1991-12-01' , '女');
insert into Student values('2019006' , '吴兰' , '1992-03-01' , '女');
insert into Student values('2019007' , '郑竹' , '1989-07-01' , '女');
insert into Student values('2019008' , '王菊' , '1990-01-20' , '女');

-- 教师表测试数据
insert into Teacher values('1001' , '张三');
insert into Teacher values('1002' , '李四');
insert into Teacher values('1003' , '王五');

-- 课程表测试数据
insert into Course values('101' , '语文' , '1002');
insert into Course values('102' , '数学' , '1001');
insert into Course values('103' , '英语' , '1003');

-- 成绩表测试数据
insert into Score values('2019001' , '101' , 80);
insert into Score values('2019001' , '102' , 90);
insert into Score values('2019001' , '103' , 99);
insert into Score values('2019002' , '101' , 70);
insert into Score values('2019002' , '102' , 60);
insert into Score values('2019002' , '103' , 80);
insert into Score values('2019003' , '101' , 80);
insert into Score values('2019003' , '102' , 80);
insert into Score values('2019003' , '103' , 80);
insert into Score values('2019004' , '101' , 50);
insert into Score values('2019004' , '102' , 30);
insert into Score values('2019004' , '103' , 20);
insert into Score values('2019005' , '101' , 76);
insert into Score values('2019005' , '102' , 87);
insert into Score values('2019006' , '101' , 31);
insert into Score values('2019006' , '103' , 34);
insert into Score values('2019007' , '102' , 89);
insert into Score values('2019007' , '103' , 98);

View Code

SQL的50练习题详解

-- 做题于2019-11-19

-- 学生表
select * from student;
-- 教师表
select * from teacher;
-- 课程表
select * from course;
-- 成绩表
select * from score;

-- 1、查询"101"课程比"102"课程成绩高的学生的信息及课程分数 
SELECT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex,
    course.CrName,
    SrScore
FROM
    student
LEFT JOIN score ON student.StuNum = score.StuNum
LEFT JOIN course ON score.CrNum = course.CrNum
WHERE student.StuNum IN(
            SELECT 
                a.StuNum 
            FROM
                (SELECT StuNum, SrScore AS a_score FROM score WHERE CrNum = '101') a
            INNER JOIN 
                (SELECT StuNum, SrScore AS b_score FROM score WHERE CrNum = '102') b ON a.StuNum = b.StuNum
            WHERE a_score > b_score
);

-- 2、查询"101"课程比"102"课程成绩低的学生的信息及课程分数
SELECT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex,
    course.CrName,
    SrScore
FROM
    student
LEFT JOIN score ON student.StuNum = score.StuNum
LEFT JOIN course ON score.CrNum = course.CrNum
WHERE student.StuNum IN(
            SELECT 
                a.StuNum 
            FROM
                (SELECT StuNum, SrScore AS a_score FROM score WHERE CrNum = '101') a
            INNER JOIN 
                (SELECT StuNum, SrScore AS b_score FROM score WHERE CrNum = '102') b ON a.StuNum = b.StuNum
            WHERE a_score < b_score
);

-- 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
SELECT
    A.StuNum,
    A.StuName,
    B.avg_SrScore
FROM 
    student A
INNER JOIN 
    (SELECT StuNum, AVG(SrScore) AS avg_SrScore FROM score GROUP BY StuNum HAVING AVG(SrScore) >= 60) B 
ON A.StuNum = B.StuNum;

-- 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)
SELECT
    A.StuNum,
    A.StuName,
    B.avg_SrScore
FROM 
    student A
INNER JOIN 
    (SELECT StuNum, AVG(SrScore) AS avg_SrScore FROM score GROUP BY StuNum HAVING AVG(SrScore) < 60) B 
ON A.StuNum = B.StuNum;

-- 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.StuNum,
    A.StuName,
    B.count_StuNum '选课数',
    B.sum_SrScore '总成绩'
FROM
    student A
RIGHT JOIN (
    SELECT StuNum, COUNT(StuNum) count_StuNum, SUM(SrScore) sum_SrScore FROM score GROUP BY StuNum ) B 
ON A.StuNum = B.StuNum;

-- 6、查询"李"姓老师的数量
SELECT COUNT(1) FROM teacher WHERE TchName LIKE '李%';

-- 7、查询学过"张三"老师授课的同学的信息
SELECT
    StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE StuNum IN(
            SELECT StuNum FROM score 
            WHERE CrNum = (SELECT CrNum FROM course INNER JOIN teacher ON course.TchNum = teacher.TchNum AND teacher.TchName = '张三')
);

-- 8、查询没学过"张三"老师授课的同学的信息
SELECT
    StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE StuNum NOT IN(
            SELECT DISTINCT StuNum FROM score 
            WHERE CrNum = (SELECT CrNum FROM course INNER JOIN teacher ON course.TchNum = teacher.TchNum AND teacher.TchName = '张三')
);
-- 9、查询学过编号为"101"并且也学过编号为"102"的课程的同学的信息
SELECT
    StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE 
    StuNum IN(SELECT StuNum FROM score WHERE CrNum = '101')
AND 
    StuNum IN(SELECT StuNum FROM score WHERE CrNum = '102');

-- 10、查询学过编号为"101"但是没有学过编号为"102"的课程的同学的信息
SELECT
    StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE
    StuNum IN(SELECT StuNum FROM score WHERE CrNum = '101')
AND 
    StuNum NOT IN(SELECT StuNum FROM score WHERE CrNum = '102');
-- 11、查询没有学全所有课程的同学的信息
SELECT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
LEFT JOIN score ON student.StuNum = score.StuNum
GROUP BY StuNum HAVING count(1) < (SELECT count(1) FROM course);

-- 12、查询至少有一门课与学号为"2019001"的同学所学相同的同学的信息
SELECT DISTINCT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
LEFT JOIN score ON student.StuNum = score.StuNum AND CrNum IN(SELECT CrNum FROM score WHERE StuNum = '2019001');

-- 13、查询和"2019001"号的同学学习的课程完全相同的其他同学的信息
SELECT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
LEFT JOIN score ON student.StuNum = score.StuNum
GROUP BY student.StuNum
HAVING group_concat(score.CrNum) = (
                SELECT group_concat(score.CrNum) 
                FROM 
                    student 
                LEFT JOIN score 
                ON student.StuNum = score.StuNum 
                WHERE student.StuNum = '2019001');

-- 14、查询没学过"张三"老师讲授的任一门课程的学生姓名
SELECT DISTINCT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE
    StuNum NOT IN(
        SELECT StuNum FROM score WHERE CrNum = (
            SELECT CrNum FROM teacher INNER JOIN course ON teacher.TchNum = course.TchNum AND teacher.TchName = '张三'
        )
);

-- 15、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
SELECT
    student.StuNum,
    student.StuName,
    avg(SrScore) AS '平均成绩'
FROM student
LEFT JOIN score ON student.StuNum = score.StuNum
WHERE student.StuNum IN(SELECT StuNum FROM score WHERE SrScore < 60 GROUP BY StuNum HAVING count(1) >= 2);

-- 16、检索"101"课程分数小于60，按分数降序排列的学生信息
SELECT 
    StuNum,
    StuName,
    StuBirth,
    StuSex
FROM
    student
WHERE StuNum IN(SELECT StuNum FROM score WHERE CrNum = '101' AND SrScore < 60);

-- 17、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

SELECT
    student.StuNum,
    MAX(CASE score.CrNum WHEN '101' THEN score.SrScore ELSE 0 END) '语文',
    MAX(CASE score.CrNum WHEN '102' THEN score.SrScore ELSE 0 END) '数学',
    MAX(CASE score.CrNum WHEN '103' THEN score.SrScore ELSE 0 END) '英语',
    AVG(SrScore) AS '平均成绩'
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum
GROUP BY
    score.StuNum
ORDER BY AVG(SrScore) DESC;

-- 18.查询各科成绩最高分、最低分和平均分：显示形式：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

SELECT
    course.CrNum,
    course.CrName,
    MAX(score.SrScore) '最高分',
    MIN(score.SrScore) '最低分',
    ROUND(100*((SELECT count(1) FROM score WHERE score.CrNum = course.CrNum AND SrScore >= 60)
                            /(SELECT count(1) FROM score WHERE score.CrNum = course.CrNum)),2) '及格率',
    ROUND(100*((SELECT count(1) FROM score WHERE score.CrNum = course.CrNum AND SrScore >= 70 AND SrScore < 80)
                            /(SELECT count(1) FROM score WHERE score.CrNum = course.CrNum)),2) '中等率',
    ROUND(100*((SELECT count(1) FROM score WHERE score.CrNum = course.CrNum AND SrScore >= 80 AND SrScore < 90)
                            /(SELECT count(1) FROM score WHERE score.CrNum = course.CrNum)),2) '优良率',
    ROUND(100*((SELECT count(1) FROM score WHERE score.CrNum = course.CrNum AND SrScore >= 90 AND SrScore <= 100)
                            /(SELECT count(1) FROM score WHERE score.CrNum = course.CrNum)),2) '优秀率'
FROM
    course
INNER JOIN score ON course.CrNum = score.CrNum
GROUP BY course.CrNum;

-- 19、按各科成绩进行排序，并显示排名
-- 方式一
select StuNum, CrNum, SrScore, (@rank := @rank + 1) AS rank from (score, (SELECT @rank := 0) b) order by CrNum, SrScore desc;
-- 方式二
select * from (
select StuNum, CrNum, SrScore, (@i :=@i + 1) AS rank from 
 ((select StuNum,CrNum,SrScore from score where CrNum = '101' order by SrScore desc) a, (SELECT @i := 0) b)
UNION ALL
select StuNum, CrNum, SrScore, (@j :=@j + 1) AS rank from 
 ((select StuNum,CrNum,SrScore from score where CrNum = '102' order by SrScore desc) a, (SELECT @j := 0) b)
UNION ALL
select StuNum, CrNum, SrScore, (@k :=@k + 1) AS rank from 
 ((select StuNum,CrNum,SrScore from score where CrNum = '103' order by SrScore desc) a, (SELECT @k := 0) b)
) T;

-- 20、查询学生的总成绩并进行排名
select StuNum, SUM(SrScore) as '总成绩' from score GROUP BY StuNum order by '总成绩' DESC;

-- 21、查询不同老师所教不同课程平均分从高到低显示
SELECT
    teacher.TchName,
    course.CrNum,
    course.CrName,
    AVG(SrScore) '平均分'
FROM
    teacher
INNER JOIN course ON teacher.TchNum = course.TchNum
RIGHT JOIN score ON course.CrNum = score.CrNum
GROUP BY
    teacher.TchNum
ORDER BY
    AVG(SrScore) DESC;

-- 22、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
SELECT
    student.StuNum,
    StuName,
    StuBirth,
    StuSex,
    SrScore
FROM
    student
RIGHT JOIN (
    (SELECT StuNum,SrScore FROM score WHERE CrNum = '101' ORDER BY SrScore DESC LIMIT 1, 2)
    UNION ALL
    (SELECT StuNum,SrScore FROM score WHERE CrNum = '102' ORDER BY SrScore DESC LIMIT 1, 2)
    UNION ALL
    (SELECT StuNum,SrScore FROM score WHERE CrNum = '103' ORDER BY SrScore DESC LIMIT 1, 2)
) Sr ON student.StuNum = Sr.StuNum;

-- 23、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]及所占百分比
SELECT
    course.CrNum,
    course.CrName,
    ((select count(1) from score where score.CrNum = course.CrNum and SrScore >= 85 and SrScore <= 100)
        /(select count(1) from score where score.CrNum = course.CrNum)) '[85,100]',
    ((select count(1) from score where score.CrNum = course.CrNum and SrScore >= 70 and SrScore < 85)
        /(select count(1) from score where score.CrNum = course.CrNum)) '[70,85]',
    ((select count(1) from score where score.CrNum = course.CrNum and SrScore >= 60 and SrScore < 70)
        /(select count(1) from score where score.CrNum = course.CrNum)) '[60,70]',
    ((select count(1) from score where score.CrNum = course.CrNum and SrScore < 60)
        /(select count(1) from score where score.CrNum = course.CrNum)) '[0,60]'
FROM
    course
INNER JOIN score ON course.CrNum = score.CrNum
GROUP BY course.CrNum;

-- 24、查询学生平均成绩及其名次
SELECT
    StuNum,
    avg_SrScore '平均分',
    (@rank := @rank + 1) '排名'
FROM
    ((SELECT StuNum, AVG(SrScore) avg_SrScore FROM score GROUP BY StuNum ORDER BY AVG(SrScore) DESC) a,
     (SELECT @rank := 0) b
    );

-- 25、查询各科成绩前三名的记录
select * from (
    (select * from score where CrNum = '101' order by SrScore desc LIMIT 3)
    UNION
    (select * from score where CrNum = '102' order by SrScore desc LIMIT 3)
    UNION
    (select * from score where CrNum = '103' order by SrScore desc LIMIT 3)
) T;

-- 26、查询每门课程被选修的学生数
SELECT
    course.CrNum,
    course.CrName,
    count(1)
FROM
    course
INNER JOIN score ON course.CrNum = score.CrNum
GROUP BY CrNum;

-- 27、查询出只有两门课程的全部学生的学号和姓名
SELECT
    StuNum,
    StuName
FROM
    student
WHERE
    StuNum IN (SELECT StuNum FROM score GROUP BY StuNum HAVING count(1) = 2);

-- 28、查询男生、女生人数
SELECT StuSex, count(1) FROM student GROUP BY StuSex;

-- 29、查询名字中含有"风"字的学生信息
SELECT StuNum,StuName,StuBirth,StuSex FROM student where StuName like '%风%';

-- 30、查询同名同姓学生名单，并统计同名人数
SELECT StuName, count(1) FROM student group by StuName having count(1) > 1;

-- 31、查询1990年出生的学生名单
SELECT StuNum,StuName,StuBirth,StuSex FROM student WHERE YEAR(StuBirth) = '1990';

-- 32、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
SELECT CrNum, AVG(SrScore) '平均成绩' FROM score GROUP BY CrNum ORDER BY AVG(SrScore) DESC, CrNum;

-- 33、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
    student.StuNum,
    student.StuName,
    AVG(SrScore) '平均成绩'
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum
GROUP BY student.StuNum
HAVING AVG(SrScore) >= 85;

-- 34、查询课程名称为"数学"，且分数低于60的学生姓名和分数
SELECT
    StuName,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum AND SrScore < 60
INNER JOIN course ON score.crnum = course.CrNum AND CrName = '数学';

-- 35、查询所有学生的课程及分数情况
SELECT
    student.StuNum,
    StuName,
    course.CrNum,
    CrName,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum
INNER JOIN course ON score.crnum = course.CrNum;

-- 36、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
    StuName,
    CrName,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum AND SrScore >= 70
INNER JOIN course ON score.crnum = course.CrNum;

SELECT
    StuName,
    MAX(case course.CrName WHEN '语文' THEN SrScore ELSE 0 END) '语文',
    MAX(case course.CrName WHEN '数学' THEN SrScore ELSE 0 END) '数学',
    MAX(case course.CrName WHEN '英语' THEN SrScore ELSE 0 END) '英语'
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum AND SrScore >= 70
INNER JOIN course ON score.CrNum = course.CrNum
GROUP BY StuName;

-- 37、查询不及格的课程
SELECT
    StuName,
    CrName,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum AND SrScore < 60
INNER JOIN course ON score.CrNum = course.CrNum;

-- 38、查询课程编号为"101"且课程成绩在80分以上的学生的学号和姓名
SELECT
    student.StuNum,
    StuName,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum AND SrScore >= 80 AND CrNum = '101';

-- 39、求每门课程的学生人数
SELECT
    course.CrNum,
    CrName,
    count(1)
FROM
    course
INNER JOIN score ON course.CrNum = score.CrNum GROUP BY course.CrNum;

-- 40、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
    student.StuNum,
    StuName,
    StuBirth,
    StuSex,
    SrScore
FROM
    student
INNER JOIN score ON student.StuNum = score.StuNum
INNER JOIN course ON score.CrNum = course.CrNum
INNER JOIN teacher ON course.TchNum = teacher.TchNum AND TchName = '张三'
ORDER BY SrScore DESC LIMIT 1;

-- 41、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
-- 个人理解：指同一个学生的不同学科，但考试成绩相同的数据
SELECT DISTINCT a.StuNum, a.CrNum, a.SrScore
FROM
    (SELECT StuNum, CrNum, SrScore FROM score) a
INNER JOIN 
    (SELECT StuNum, CrNum, SrScore FROM score) b 
ON a.StuNum = b.StuNum AND a.CrNum != b.CrNum AND a.SrScore = b.SrScore;

-- 42、查询每门功课成绩最好的前两名
-- 方式一
select * from (
    (select * from score where CrNum = '101' order by SrScore desc LIMIT 2)
    UNION
    (select * from score where CrNum = '102' order by SrScore desc LIMIT 2)
    UNION
    (select * from score where CrNum = '103' order by SrScore desc LIMIT 2)
) T;
-- 方式二 更具有普适性
SELECT
    StuNum,
    CrNum,
    SrScore
FROM
    score a
WHERE
    (SELECT COUNT(1) FROM score b WHERE b.CrNum = a.CrNum AND b.SrScore >= a.SrScore) <= 2
ORDER BY a.CrNum;

-- 43、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
SELECT CrNum, count(1) FROM score GROUP BY CrNum HAVING count(1) > 5 ORDER BY count(1) DESC, CrNum ASC;

-- 44、检索至少选修两门课程的学生学号
select StuNum from score group by StuNum having COUNT(1) >= 2;

-- 45、查询选修了全部课程的学生信息
SELECT StuNum FROM score GROUP BY StuNum HAVING COUNT(1) = (SELECT count(1) FROM course);

-- 46、查询各学生的年龄
SELECT (YEAR(NOW())-YEAR(StuBirth)) '年龄' FROM student;

-- 47、查询本周过生日的学生
SELECT StuNum,StuName,StuBirth,StuSex FROM student WHERE WEEK(StuBirth)=WEEK(NOW());

-- 48、查询下周过生日的学生
SELECT StuNum,StuName,StuBirth,StuSex FROM student WHERE WEEK(StuBirth)= (WEEK(NOW()) + 1);

-- 49、查询本月过生日的学生
SELECT StuNum,StuName,StuBirth,StuSex FROM student WHERE MONTH(StuBirth)= MONTH(NOW());

-- 50、查询下月过生日的学生
SELECT StuNum,StuName,StuBirth,StuSex FROM student WHERE MONTH(StuBirth)= (MONTH(NOW()) + 1);

View Code

posted @ 2019-11-19 15:53 第五个账号阅读(292) 评论(0) 收藏举报

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