Daniel Liu

I Need You To Tell Me That I’m A Good Person.

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MySQL练习

2021年3月9日

MySQL练习

数据库初始化

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drop table if exists t_score;
drop table if exists t_courses;
drop table if exists t_students;
drop table if exists t_teachers;

-- 学生表
CREATE TABLE `Student`(
    `s_id` VARCHAR(20),
    `s_name` VARCHAR(20) NOT NULL DEFAULT '',
    `s_birth` VARCHAR(20) NOT NULL DEFAULT '',
    `s_sex` VARCHAR(10) NOT NULL DEFAULT '',
    PRIMARY KEY(`s_id`)
);
-- 课程表
CREATE TABLE `Course`(
    `c_id`  VARCHAR(20),
    `c_name` VARCHAR(20) NOT NULL DEFAULT '',
    `t_id` VARCHAR(20) NOT NULL,
    PRIMARY KEY(`c_id`)
);
-- 教师表
CREATE TABLE `Teacher`(
    `t_id` VARCHAR(20),
    `t_name` VARCHAR(20) NOT NULL DEFAULT '',
    PRIMARY KEY(`t_id`)
);
-- 成绩表
CREATE TABLE `Score`(
    `s_id` VARCHAR(20),
    `c_id`  VARCHAR(20),
    `s_score` INT(3),
    PRIMARY KEY(`s_id`,`c_id`)
);
-- 插入学生表测试数据
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);

练习题

  1. 查询"01"课程比"02"课程成绩高的学生的信息及课程分数

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    select stu.stu_id, stu.stu_name, stu.birthday, stu.stu_gender,
        ifnull(sc1.score, 0) as '1课程分数', ifnull(sc2.score, 0) as '2课程分数'
    from t_students stu
    left join t_score sc1 on stu.stu_id = sc1.stu_id and sc1.course_id = 1
    left join t_score sc2 on stu.stu_id = sc2.stu_id and sc2.course_id = 2
    where ifnull(sc1.score, 0) > ifnull(sc2.score, 0);

  2. 查询"01"课程比"02"课程成绩低的学生的信息及课程分数

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    select stu.stu_id, stu.stu_name, stu.birthday, stu.stu_gender,
        ifnull(sc1.score, 0) as '1课程分数', ifnull(sc2.score, 0) as '2课程分数'
    from t_students stu
    left join t_score sc1 on stu.stu_id = sc1.stu_id and sc1.course_id = 1
    left join t_score sc2 on stu.stu_id = sc2.stu_id and sc2.course_id = 2
    where ifnull(sc1.score, 0) < ifnull(sc2.score, 0);

  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

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    select stu.stu_id, stu.stu_name, round(avg(sc.score), 2) as avg_score
    from t_students stu
    left join t_score sc on stu.stu_id = sc.stu_id
    group by stu.stu_id, stu.stu_name
    having avg_score >= 60;

  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

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    select stu.stu_id, stu.stu_name, round(ifnull(avg(sc.score), 0), 2) as avg_score
    from t_students stu
    left join t_score sc on stu.stu_id = sc.stu_id
    group by stu.stu_id, stu.stu_name
    having avg_score < 60;

  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

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    select stu.stu_id, stu.stu_name, 
        count(sc.course_id) as 'qty_course', -- 选课数量
        ifnull(sum(sc.score), 0) as 'sum_score' -- 总分数
    from t_students stu
    left join t_score sc on stu.stu_id = sc.stu_id
    group by stu.stu_id, stu.stu_name;

  6. 查询"李"姓老师的数量

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    select count(0) from t_teachers
    where teacher_name like '李%';

  7. 查询学过"张三"老师授课的同学的信息

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    select stu.* from t_students stu
    where stu.stu_id in (
        select sc.stu_id from t_score sc
        left join t_courses cou on sc.course_id = cou.course_id
        left join t_teachers te on cou.teacher_id = te.teacher_id
        where te.teacher_name = '贝吉塔'
    );

  8. 查询没学过"张三"老师授课的同学的信息

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    select stu.* from t_students stu
    where stu.stu_id not in (
        select sc.stu_id from t_score sc
        left join t_courses cou on sc.course_id = cou.course_id
        left join t_teachers te on cou.teacher_id = te.teacher_id
        where te.teacher_name = '贝吉塔'
    );

  9. 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

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    select stu_id, stu_name, birthday, stu_gender
    from t_students
    where stu_id in (
        select stu_id
        from t_score
        where course_id = 1)
    and stu_id in (
        select stu_id
        from t_score
        where course_id = 2);

  10. 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

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    select stu_id, stu_name, birthday, stu_gender
    from t_students
    where stu_id in (
        select stu_id
        from t_score
        where course_id = 1)
    and stu_id not in (
        select stu_id
        from t_score
        where course_id = 2);

  11. 查询没有学全所有课程的同学的信息

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    select student_id, student_name
    from tb_student
    where student_id in (
        select stu.student_id
        from tb_student stu
        left join tb_score sc on stu.student_id = sc.student_id
        group by student_id
        having count(course_id) < (
            select count(0)
            from tb_course
        )
    );

  12. 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

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    select * from t_students
    where stu_id in (
    	select stu_id from t_score
    	where course_id in (
    		select course_id from t_score where stu_id = 1
    	) and stu_id != 1
    	group by stu_id
    );

  13. 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

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    select * from t_students where stu_id in (
    	select temp.stu_id from (
    		select sc.stu_id, group_concat(crs.course_name) as courses
    		from t_score sc
    		left join t_courses crs on sc.course_id = crs.course_id
    		group by sc.stu_id
    	) temp where temp.courses = (
    		select group_concat(crs.course_name) as courses
    		from t_score sc
    		left join t_courses crs on sc.course_id = crs.course_id
    		group by sc.stu_id
    		having sc.stu_id = 1
    	) and temp.stu_id != 1
    );

  14. 查询没学过"张三"老师讲授的任一门课程的学生姓名

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    select stu.stu_name from t_students stu where stu.stu_id not in (
        select sc.stu_id from t_score sc -- 学过贝吉塔教的课的学生id
        left join t_courses cou on sc.course_id = cou.course_id
        left join t_teachers tc on cou.teacher_id = tc.teacher_id
        where tc.teacher_name = '贝吉塔'
    );

  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

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    select stu.stu_id, stu.stu_name, avg(sc.score)
    from t_students stu
    left join  t_score sc on stu.stu_id = sc.stu_id
    group by stu.stu_id, stu.stu_name
    having sum(
    	case 
    	when ifnull(sc.score, 0) < 60 then 1
    	else 0 end
    ) >= 2;

  16. 检索"01"课程分数小于60，按分数降序排列的学生信息

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    select stu.*, sum(sc.score) as score_sum
    from t_students stu
    left join t_score sc on stu.stu_id = sc.stu_id
    where stu.stu_id in (
    	select stu_id from t_score
    	where course_id = 1 and score < 60
    ) group by stu.stu_id
    order by score_sum desc;

  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

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    select stu.stu_id, stu.stu_name,
      ifnull(sc1.score, 0) as yw_score, -- 语文分数
      ifnull(sc2.score, 0) as sx_score, -- 数学分数
      ifnull(sc3.score, 0) as yy_score, -- 英语分数
      round(ifnull(avg_t.avg_score, 0), 2) as avg_score
    from t_students stu
    left join t_score sc1 on stu.stu_id = sc1.stu_id and sc1.course_id = 1 -- 语文成绩表
    left join t_score sc2 on stu.stu_id = sc2.stu_id and sc2.course_id = 2 -- 数学成绩表
    left join t_score sc3 on stu.stu_id = sc3.stu_id and sc3.course_id = 3 -- 英语成绩表
    left join ( -- 子查询, 临时表
        select stu_id, avg(score) as avg_score -- 平均分
        from t_score
        group by stu_id
        order by avg_score
        ) avg_t on stu.stu_id = avg_t.stu_id
    order by avg_t.avg_score desc;

  18. 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

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    select sc.course_id, crs.course_name,
        max(sc.score) as max_score,
        min(sc.score) as min_score,
        avg(sc.score) as avg_score,
        sum(sc.score >= 60) / 8 as pass_per,
        sum(sc.score >= 70 and sc.score < 80) / 8 as medium_per,
        sum(
        	case
        	when sc.score >= 80 and sc.score < 90 then 1
        	else 0
        	end
        ) / 8 as good_per,
        sum(
        	case
        	when sc.score >= 90 then 1
        	else 0
        	end
        ) / 8 as perfect_per
    from t_score sc
    right join t_courses crs on sc.course_id = crs.course_id
    group by sc.course_id, crs.course_name;

  19. 按各科成绩进行排序，并显示排名

  20. 查询学生的总成绩并进行排名

    1. 查询学生的总成绩
    2. 查询学生的总成绩并进行排名，sql 2000用子查询完成，分总分重复时保留名次空缺和不保留名次空缺两种。
    3. 查询学生的总成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分总分重复时保留名次空缺和不保留名次空缺两种。

  21. 查询不同老师所教不同课程平均分从高到低显示

  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

  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

    1. 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]
    2. 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]及所占百分比

  24. 查询学生平均成绩及其名次

    1. 查询学生的平均成绩并进行排名，sql 2000用子查询完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。
    2. 查询学生的平均成绩并进行排名，sql 2005用rank,DENSE_RANK完成，分平均成绩重复时保留名次空缺和不保留名次空缺两种。

  25. 查询各科成绩前三名的记录

    1. 分数重复时保留名次空缺
    2. 分数重复时不保留名次空缺，合并名次

  26. 查询每门课程被选修的学生数

  27. 查询出只有两门课程的全部学生的学号和姓名

  28. 查询男生. 女生人数

  29. 查询名字中含有"风"字的学生信息

  30. 查询同名同性学生名单，并统计同名人数

  31. 查询1990年出生的学生名单

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SELECT *
FROM t_students
WHERE EXTRACT(YEAR FROM birthday) = 1990;
  1. 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
  2. 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
  3. 查询课程名称为"数学"，且分数低于60的学生姓名和分数
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SELECT
  t_students.stu_name,
  t_score.score
FROM t_score
  CROSS JOIN t_courses ON t_score.course_id = t_courses.course_id AND t_courses.course_name = '数学'
  CROSS JOIN t_students ON t_score.stu_id = t_students.stu_id
WHERE score < 60
  1. 查询所有学生的课程及分数情况；
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SELECT stu_name,score,course_name FROM t_students
LEFT JOIN t_score ON t_students.stu_id = t_score.stu_id
LEFT JOIN t_courses ON t_score.course_id = t_courses.course_id;
  1. 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；
  2. 查询不及格的课程
  3. 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；
  4. 求每门课程的学生人数
  5. 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
    1. 当最高分只有一个时
    2. 当最高分出现多个时
  6. 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
  7. 查询每门功成绩最好的前两名
  8. 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
  9. 检索至少选修两门课程的学生学号
  10. 查询选修了全部课程的学生信息
  11. 查询各学生的年龄
    1. 只按照年份来算
    2. 按照出生日期来算，当前月日 < 出生年月的月日则，年龄减一
  12. 查询本周过生日的学生
  13. 查询下周过生日的学生
  14. 查询本月过生日的学生
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SELECT *
FROM t_students
WHERE EXTRACT(MONTH FROM birthday) = EXTRACT(MONTH FROM curdate());
  1. 查询下月过生日的学生
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SELECT *
FROM t_students
WHERE EXTRACT(MONTH FROM birthday) = EXTRACT(MONTH FROM curdate()) + 1
      OR EXTRACT(MONTH FROM birthday) = 1 AND EXTRACT(MONTH FROM curdate()) = 12;
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1 MySQL练习
1.1 数据库初始化
1.2 练习题