50道SQL经典题

题目转载自50道SQL练习题。答案大都是我自己写的，部分答案借鉴了上文中提供的答案。另外，我在编写本 文时将题目大致按照由易到难的顺序做了重新编排。

由于我在数据库方面尚处于入门阶段，因此若是您发现本文中有任何错误或者可以改进的地方都请联系并告知我。

创建测试数据

创建student表：

CREATE TABLE student(
    id UNSIGNED BIGINT NOT NULL PRIMARY KEY,
    name NVARCHAR(4) NOT NULL, 
    birthday DATETIME NOT NULL, 
    sex NCHAR(2) NOT NULL
);
INSERT INTO student VALUES(1, '赵雷' , '1990-01-01' , '男');
INSERT INTO student VALUES(2, '钱电' , '1990-12-21' , '男');
INSERT INTO student VALUES(3, '孙风' , '1990-05-20' , '男');
INSERT INTO student VALUES(4, '李云' , '1990-08-06' , '男');
INSERT INTO student VALUES(5, '周梅' , '1991-12-01' , '女');
INSERT INTO student VALUES(6, '吴兰' , '1992-03-01' , '女');
INSERT INTO student VALUES(7, '郑竹' , '1989-07-01' , '女');
INSERT INTO student VALUES(8, '张三' , '2017-12-20' , '女');
INSERT INTO student VALUES(9, '李四' , '2017-12-25' , '女');
INSERT INTO student VALUES(10, '李四' , '2017-12-30' , '女');
INSERT INTO student VALUES(11, '赵六' , '2017-01-01' , '女');
INSERT INTO student VALUES(12, '孙七' , '2018-01-01' , '女');

创建course表：

CREATE TABLE course(
    id UNSIGNED BIGINT NOT NULL PRIMARY KEY,
    name NVARCHAR(4) NOT NULL,
    teacher_id UNSIGNED BIGINT
);
INSERT INTO course VALUES(1, '语文' , 2);
INSERT INTO course VALUES(2, '数学' , 1);
INSERT INTO course VALUES(3, '英语' , 3);

创建teacher表：

CREATE TABLE teacher(
    id UNSIGNED BIGINT NOT NULL PRIMARY KEY,
    name NVARCHAR(4)
);
INSERT INTO teacher VALUES(1, '张三');
INSERT INTO teacher VALUES(2, '李四');
INSERT INTO teacher VALUES(3, '王五');

创建grade表（成绩表）：

CREATE TABLE grade(
    id UNSIGNED BIGINT NOT NULL PRIMARY KEY,
    student_id UNSIGNED BIGINT NOT NULL,
    course_id UNSIGNED BIGINT NOT NULL,
    score DECIMAL(5,2)
);
INSERT INTO grade VALUES(1, 1, 1, 80);
INSERT INTO grade VALUES(2, 1, 2, 90);
INSERT INTO grade VALUES(3, 1, 3, 99);
INSERT INTO grade VALUES(4, 2, 1, 70);
INSERT INTO grade VALUES(5, 2, 2, 60);
INSERT INTO grade VALUES(6, 2, 3, 80);
INSERT INTO grade VALUES(7, 3, 1, 80);
INSERT INTO grade VALUES(8, 3, 2, 80);
INSERT INTO grade VALUES(9, 3, 3, 80);
INSERT INTO grade VALUES(10, 4, 1, 50);
INSERT INTO grade VALUES(11, 4, 2, 30);
INSERT INTO grade VALUES(12, 4, 3, 20);
INSERT INTO grade VALUES(13, 5, 1, 76);
INSERT INTO grade VALUES(14, 5, 2, 87);
INSERT INTO grade VALUES(15, 6, 1, 31);
INSERT INTO grade VALUES(16, 6, 3, 34);
INSERT INTO grade VALUES(17, 7, 2, 89);
INSERT INTO grade VALUES(18, 7, 3, 98);

题目及答案

1. 查询「李」姓老师的数量

   SELECT COUNT(*) FROM teacher
   WHERE name LIKE "李%";
   

2. 查询 1990 年出生的学生名单

   SELECT * FROM student
   WHERE YEAR(birthday) = 1990;
   

3. 查询名字中含有「风」字的学生信息

   SELECT * FROM student
   WHERE name LIKE "%风%";
   

4. 求每门课程的学生人数

   SELECT grade.course_id, COUNT(student_id) FROM grade
   GROUP BY course_id;
   

5. 查询本月过生日的学生

   SELECT * FROM student
   WHERE MONTH(NOW()) = MONTH(birthday);
   

6. 查询下月过生日的学生

   SELECT * FROM student
   WHERE MONTH(NOW()) + 1 = MONTH(birthday);
   

7. 查询本周过生日的学生

   SELECT * FROM student
   WHERE WEEKOFYEAR(NOW()) = WEEKOFYEAR(birthday);
   

8. 查询下周过生日的学生

   SELECT * FROM student
   WHERE WEEKOFYEAR(NOW()) + 1 = WEEKOFYEAR(birthday);
   

9. 查询各学生的年龄，只按年份来算

   SELECT *, YEAR(NOW()) - YEAR(birthday) AS 年龄 FROM student;
   

10. 按照出生日期来算，当前月日小于出生年月的月日则，年龄减一

    SELECT *, TIMESTAMPDIFF(YEAR, birthday, NOW()) AS 年龄 FROM student;
    

11. 检索至少选修两门课程的学生学号

    SELECT student_id FROM grade
    GROUP BY student_id
    HAVING COUNT(course_id) >= 2;
    

12. 统计每门课程的学生选修人数（超过5人的课程才统计）

    SELECT course_id, COUNT(*) FROM grade
    GROUP BY course_id
    HAVING COUNT(*) > 5;
    

13. 查询存在不及格成绩的课程

    SELECT course_id FROM grade
    GROUP BY course_id
    HAVING COUNT(score < 60) > 0;
    

14. 查询男生、女生人数

    SELECT sex, COUNT(*) FROM student
    GROUP BY sex;
    

15. 查询每门课程被选修的学生数

    SELECT course_id, COUNT(student_id) FROM grade
    GROUP BY course_id;
    

16. 查询在grade表存在成绩的学生信息

    SELECT * FROM student
    WHERE id IN (
    SELECT student_id FROM grade
    );
    

17. 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 course_id, AVG(score) FROM grade
    GROUP BY course_id
    ORDER BY AVG(score) DESC, course_id;
    

18. 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 grade.student_id, grade.course_id as course_id1, t.course_id as course_id2, grade.score FROM grade, grade AS t
    WHERE grade.student_id = t.student_id AND grade.course_id != t.course_id AND grade.score = t.score;
    

19. 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）

    SELECT student.*, grade.course_id, grade.score FROM student
    LEFT JOIN grade ON student.id = grade.student_id;
    

20. 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 student.id, student.name FROM student, grade
    WHERE student.id = grade.student_id AND grade.course_id = 1 AND grade.score >= 80;
    

21. 查询每门功成绩最好的前两名

    SELECT * FROM grade
    WHERE (
    SELECT COUNT(*) FROM grade AS t
    WHERE t.course_id = grade.course_id AND t.score > grade.score
    ) < 2
    ORDER BY course_id, score DESC;
    

22. 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 student.name as student_name, course.name as course_name, grade.score FROM student, course, grade
    WHERE grade.score >= 70 AND student.id = grade.student_id AND grade.course_id = course.id;
    

23. 查询出只选修两门课程的学生学号和姓名

    SELECT t.student_id, student.name FROM (
    SELECT student_id FROM grade
    GROUP BY student_id
    HAVING COUNT(course_id) = 2
    ) AS t 
    LEFT JOIN student ON t.student_id = student.id;
    

24. 查询同名同姓学生名单，并统计同名人数

    SELECT student.*, t.num FROM (
    SELECT name, COUNT(*) AS num FROM student
    GROUP BY name
    HAVING COUNT(*) > 1
    ) AS t, student
    WHERE student.name = t.name;
    

25. 查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

    SELECT student.name, grade.score FROM grade, student, course
    WHERE course.name = "数学" AND course.id = grade.course_id AND grade.student_id = student.id AND grade.score < 60;
    

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 t.*, student.name FROM (
    SELECT student_id, AVG(score) FROM grade
    GROUP BY student_id
    HAVING AVG(score) >= 85
    ) AS t
    LEFT JOIN student ON t.student_id = student.id;
    

27. 检索1课程分数小于60，按分数降序排列的学生信息

    SELECT student.* FROM student, grade
    WHERE student.id = grade.student_id and grade.course_id = 1 and score < 60
    ORDER BY score DESC;
    

28. 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 grade.*, t.avg_score FROM 
    grade LEFT JOIN (
    SELECT student_id, AVG(score) AS avg_score FROM grade
    GROUP BY student_id
    ) AS t ON t.student_id = grade.student_id
    ORDER BY t.avg_score DESC;
    

29. 查询选修了全部课程的学生信息

    SELECT student.* FROM (
    SELECT student_id FROM grade
    GROUP BY student_id
    HAVING COUNT(*) = (
        SELECT COUNT(*) FROM course
    )
    ) AS t
    LEFT JOIN student ON t.student_id = student.id;
    

30. 查询至少有一门课与学号为1的同学所学相同的同学的信息

    SELECT DISTINCT student.* FROM student, grade
    WHERE student.id = grade.student_id AND grade.course_id IN (
    SELECT course_id FROM grade
    WHERE student_id = 1
    );
    

31. 查询没有学全所有课程的同学的信息

    SELECT * FROM student
    WHERE id NOT IN (
    SELECT student_id FROM grade
    GROUP BY student_id
    HAVING COUNT(course_id) = (
        SELECT COUNT(course_id) FROM course
    )
    );
    

32. 查询没学过”张三”老师讲授的任一门课程的学生姓名

    SELECT name FROM student
    WHERE id NOT IN (
    SELECT grade.student_id FROM grade, course, teacher
    WHERE grade.course_id = course.id AND course.teacher_id = teacher.id AND teacher.name = "张三"
    );
    

33. 查询各科成绩前三名的记录

    SELECT * FROM grade 
    WHERE (
    SELECT COUNT(*) FROM grade AS t
    WHERE grade.course_id = t.course_id AND grade.score < t.score
    ) < 3 
    ORDER BY course_id, score DESC;
    

34. 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 t1.id, t1.name, t2.course_amount, t2.sum_score FROM student AS t1
    LEFT JOIN (
    SELECT student_id, COUNT(course_id) AS course_amount, SUM(score) AS sum_score FROM grade
    GROUP BY student_id
    ) AS t2 ON t1.id = t2.student_id;
    

35. 查询学过「张三」老师授课的同学的信息

    SELECT DISTINCT student.* FROM student, grade, course, teacher
    WHERE teacher.name = "张三" AND teacher.id = course.teacher_id AND course.id = grade.course_id AND grade.student_id = student.id;
    

36. 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 t1.student_id, t2.name, t1.avg_score FROM (
    SELECT student_id, AVG(score) AS avg_score FROM grade
    GROUP BY student_id
    HAVING AVG(score) >= 60
    ) AS t1
    LEFT JOIN (
    SELECT id, name FROM student
    ) AS t2 ON t1.student_id = t2.id;
    

37. 查询1课程比2课程成绩高的学生的信息及课程分数

    SELECT t1.student_id, t1.score AS c1_score, t2.score AS c2_score FROM (
    SELECT student_id, score FROM grade
    WHERE course_id = 1
    ) AS t1, (
    SELECT student_id, score FROM grade
    WHERE course_id=2
    ) AS t2
    WHERE t1.student_id = t2.student_id AND t1.score > t2.score;
    

38. 查询同时存在1课程和2课程成绩的学生的信息及课程分数

    SELECT t1.student_id, t1.score AS c1_score, t2.score AS c2_score FROM (
    SELECT student_id, score FROM grade
    WHERE course_id=1
    ) AS t1
    INNER JOIN (
    SELECT student_id, score FROM grade
    WHERE course_id=2
    ) AS t2 ON t1.student_id = t2.student_id;
    

39. 查询存在” 01 “课程但可能不存在2课程成绩(不存在时显示为NULL）的学生的信息及课程分数

    SELECT t1.student_id, t1.score AS c1_score, t2.score AS c2_score FROM (
    SELECT student_id, score FROM grade
    WHERE course_id=1
    ) AS t1 
    LEFT JOIN (
    SELECT student_id, score FROM grade
    WHERE course_id=2
    ) AS t2 ON t1.student_id = t2.student_id;
    

40. 查询不存在1课程但存在2课程成绩的学生的信息及课程分数

    SELECT student_id, score AS c2_score FROM grade
    WHERE course_id = 2 AND student_id NOT IN (
    SELECT student_id FROM grade 
    WHERE course_id = 1
    );
    

41. 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 t.student_id, student.name, t.avg_score FROM(
    SELECT student_id, AVG(score) AS avg_score FROM grade 
    WHERE score < 60 
    GROUP BY student_id 
    HAVING COUNT(score) >= 2
    ) AS t
    LEFT JOIN student ON t.student_id = student.id;
    

42. 查询和1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 student.id NOT IN (
    SELECT t2.student_id FROM grade AS t2
    WHERE t2.course_id NOT IN (
        SELECT t1.course_id FROM grade AS t1
        WHERE t1.student_id = 1
    )
    ) AND student.id != 1;
    

43. 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 grade.course_id, grade.score, student.* FROM teacher, grade, course, student
    WHERE student.id = grade.student_id AND teacher.name = "张三" AND teacher.id = course.teacher_id AND course.id = grade.course_id AND (
    SELECT COUNT(*) FROM grade AS t 
    WHERE t.course_id = grade.course_id AND t.score > grade.score
    ) = 0;
    

44. 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

    # 答案同43
    

45. 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：>=60，中等：70-80，优良：80-90，优秀：>=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

    SELECT t.*, course.name FROM (
    SELECT course_id, MAX(score) AS 最高分, MIN(score) AS 最低分, AVG(score) AS 平均分, COUNT(*) AS 选课人数, (SUM(
        CASE 
            WHEN score >= 60 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS 及格率, (SUM(
        CASE 
            WHEN score BETWEEN 70 AND 79 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS 中等率, (SUM(
        CASE 
            WHEN score BETWEEN 80 AND 89 
            THEN 1 
            ELSE 0
        END
    ) / COUNT(*)) AS 优良率, (SUM(
        CASE 
            WHEN score >= 90 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS 优秀率 FROM grade
    GROUP BY course_id
    ORDER BY COUNT(score) DESC, course_id
    ) AS t 
    LEFT JOIN course ON course.id = t.course_id;
    

46. 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

    SELECT t1.*, course.name FROM (
    SELECT course_id, (SUM(
        CASE
            WHEN score BETWEEN 85 AND 100 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS "100-85", (SUM(
        CASE 
            WHEN score BETWEEN 70 AND 84 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS "85-70",(SUM(
        CASE 
            WHEN score BETWEEN 60 AND 69 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS "70-60",(SUM(
        CASE 
            WHEN score BETWEEN 0 AND 59 
            THEN 1 
            ELSE 0 
        END
    ) / COUNT(*)) AS "60-0" FROM grade
    GROUP BY course_id
    ) AS t1
    RIGHT JOIN course ON t1.course_id = course.id;
    

47. 查询学生的总成绩，并进行排名，总分重复时保留名次空缺

    SELECT t1.*, @currank := @currank + 1 AS rank FROM (
    SELECT grade.student_id, SUM(score) FROM grade
    GROUP BY grade.student_id  
    ORDER BY SUM(score) DESC
    ) AS t1, (
    SELECT @currank := 0
    ) AS t;
    

48. 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

    SELECT t1.*, (
    CASE 
        WHEN @fontscore = t1.sumscore 
        THEN @currank
        WHEN @fontscore := t1.sumscore 
        THEN @currank := @currank+1
    END
    ) AS rank FROM (
    SELECT grade.student_id, SUM(score) AS sumscore FROM grade
    GROUP BY grade.student_id 
    ORDER BY SUM(score) DESC
    ) AS t1, (
    SELECT @currank := 0, @fontscore := NULL
    ) AS t;
    

49. 按各科成绩进行排序，并显示排名，Score重复时保留名次空缺

    SELECT grade.student_id, grade.course_id, (
    CASE 
        WHEN @pre_parent_code = grade.course_id 
        THEN @curRank := @curRank + 1 
        WHEN @pre_parent_code := grade.course_id 
        THEN @curRank := 1
    END AS rank, grade.score FROM (
    SELECT @curRank := 0, @pre_parent_code := ''
    ) AS t, grade
    ORDER BY grade.course_id, grade.score DESC;
    

50. 按各科成绩进行排序，并显示排名，Score重复时合并名次

    SELECT grade.student_id, grade.course_id, (
    CASE 
        WHEN @pre_parent_code = grade.course_id 
        THEN (
            CASE
                WHEN @prefontscore = grade.score
                THEN @curRank 
                WHEN @prefontscore := grade.score 
                THEN @curRank := @curRank + 1 
            END
        ) 
        WHEN @prefontscore := grade.score 
        THEN @curRank := 1
    END
    ) AS rank, grade.score, @pre_parent_code := grade.course_id FROM (
    SELECT @curRank := 0, @pre_parent_code := '', @prefontscore := NULL
    ) AS t, grade
    ORDER BY grade.course_id, grade.score DESC;