mysql练习题

一、表关系

请创建如下表，并创建相关约束

 

 

 

二、操作表

1、自行创建测试数据

/*
 Navicat Premium Data Transfer

 Source Server         : localhost
 Source Server Type    : MySQL
 Source Server Version : 50624
 Source Host           : localhost
 Source Database       : sqlexam

 Target Server Type    : MySQL
 Target Server Version : 50624
 File Encoding         : utf-8

 Date: 10/21/2016 06:46:46 AM
*/

SET NAMES utf8;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
--  Table structure for `class`
-- ----------------------------
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `caption` varchar(32) NOT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `class`
-- ----------------------------
BEGIN;
INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');
COMMIT;

-- ----------------------------
--  Table structure for `course`
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `cname` varchar(32) NOT NULL,
  `teacher_id` int(11) NOT NULL,
  PRIMARY KEY (`cid`),
  KEY `fk_course_teacher` (`teacher_id`),
  CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `course`
-- ----------------------------
BEGIN;
INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
COMMIT;

-- ----------------------------
--  Table structure for `score`
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  `num` int(11) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_score_student` (`student_id`),
  KEY `fk_score_course` (`course_id`),
  CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`),
  CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `score`
-- ----------------------------
BEGIN;
INSERT INTO `score` VALUES ('1', '1', '1', '10'), ('2', '1', '2', '9'), ('5', '1', '4', '66'), ('6', '2', '1', '8'), ('8', '2', '3', '68'), ('9', '2', '4', '99'), ('10', '3', '1', '77'), ('11', '3', '2', '66'), ('12', '3', '3', '87'), ('13', '3', '4', '99'), ('14', '4', '1', '79'), ('15', '4', '2', '11'), ('16', '4', '3', '67'), ('17', '4', '4', '100'), ('18', '5', '1', '79'), ('19', '5', '2', '11'), ('20', '5', '3', '67'), ('21', '5', '4', '100'), ('22', '6', '1', '9'), ('23', '6', '2', '100'), ('24', '6', '3', '67'), ('25', '6', '4', '100'), ('26', '7', '1', '9'), ('27', '7', '2', '100'), ('28', '7', '3', '67'), ('29', '7', '4', '88'), ('30', '8', '1', '9'), ('31', '8', '2', '100'), ('32', '8', '3', '67'), ('33', '8', '4', '88'), ('34', '9', '1', '91'), ('35', '9', '2', '88'), ('36', '9', '3', '67'), ('37', '9', '4', '22'), ('38', '10', '1', '90'), ('39', '10', '2', '77'), ('40', '10', '3', '43'), ('41', '10', '4', '87'), ('42', '11', '1', '90'), ('43', '11', '2', '77'), ('44', '11', '3', '43'), ('45', '11', '4', '87'), ('46', '12', '1', '90'), ('47', '12', '2', '77'), ('48', '12', '3', '43'), ('49', '12', '4', '87'), ('52', '13', '3', '87');
COMMIT;

-- ----------------------------
--  Table structure for `student`
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `gender` char(1) NOT NULL,
  `class_id` int(11) NOT NULL,
  `sname` varchar(32) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_class` (`class_id`),
  CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `student`
-- ----------------------------
BEGIN;
INSERT INTO `student` VALUES ('1', '男', '1', '理解'), ('2', '女', '1', '钢蛋'), ('3', '男', '1', '张三'), ('4', '男', '1', '张一'), ('5', '女', '1', '张二'), ('6', '男', '1', '张四'), ('7', '女', '2', '铁锤'), ('8', '男', '2', '李三'), ('9', '男', '2', '李一'), ('10', '女', '2', '李二'), ('11', '男', '2', '李四'), ('12', '女', '3', '如花'), ('13', '男', '3', '刘三'), ('14', '男', '3', '刘一'), ('15', '女', '3', '刘二'), ('16', '男', '3', '刘四');
COMMIT;

-- ----------------------------
--  Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` varchar(32) NOT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

-- ----------------------------
--  Records of `teacher`
-- ----------------------------
BEGIN;
INSERT INTO `teacher` VALUES ('1', '张磊老师'), ('2', '李平老师'), ('3', '刘海燕老师'), ('4', '朱云海老师'), ('5', '李杰老师');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            A.student_id
        FROM
            (
                SELECT
                    student_id,
                    num
                FROM
                    score
                LEFT JOIN course ON score.course_id = course.cid
                WHERE
                    course.cname = '生物'
            ) AS A
        LEFT JOIN (
            SELECT
                student_id,
                num
            FROM
                score
            LEFT JOIN course ON score.course_id = course.cid
            WHERE
                course.cname = '物理'
        ) AS B ON A.student_id = B.student_id
        WHERE
            A.num > if(ISNULL(B.num),0,B.num)
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

 

3、查询平均成绩大于60分的同学的学号、姓名和平均成绩；

-- 3、查询平均成绩大于60分的同学的学号和平均成绩； 
SELECT
    T.student_id,
    student.sname,
    T.平均成绩
FROM
    (
        SELECT
            student_id,
            avg(num) AS 平均成绩
        FROM
            score
        GROUP BY
            student_id
        HAVING
            平均成绩 > 60
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

4、查询所有同学的学号、姓名、选课数、总成绩；

SELECT
    student.sid,
    student.sname,
    count(1) as 选课数,
    IFNULL(sum(num),0) as 总成绩
FROM
    student
LEFT JOIN score ON student.sid = score.student_id
GROUP BY
    sid

 

5、查询姓“李”的老师的个数；

-- 5、查询姓“李”的老师的个数；
SELECT COUNT(1) as c FROM teacher where tname LIKE '李%'

6、查询没学过“李平”老师课的同学的学号、姓名；

SELECT
    sid,
    sname
FROM
    student
WHERE
    sid NOT IN (
        SELECT
            student_id
        FROM
            score
        WHERE
            course_id IN (
                SELECT
                    cid
                FROM
                    teacher
                LEFT JOIN course ON teacher.tid = course.teacher_id
                WHERE
                    teacher.tname = '李平老师'
            )
        GROUP BY
            student_id
    )

7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；

    思路：

        先查到既选择001又选择002课程的所有同学

        根据学生进行分组，如果学生数量等于2表示，两门均已选择

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id,
            count(1) AS c
        FROM
            score
        WHERE
            course_id = 1
        OR course_id = 2
        GROUP BY
            student_id
        HAVING
            c = 2
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

8、查询学过“李平”老师所教的所有课的同学的学号、姓名；

 

    同上，只不过将001和002变成 in (叶平老师的所有课)

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id
        FROM
            score
        WHERE
            course_id IN (
                SELECT
                    cid
                FROM
                    teacher
                LEFT JOIN course ON teacher.tid = course.teacher_id
                WHERE
                    teacher.tname = "李平老师"
            )
        GROUP BY
            student_id
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；

    同第1题

SELECT
    B.student_id,
    student.sname
FROM
    (
        SELECT
            T1.student_id
        FROM
            (
                SELECT
                    student_id,
                    num AS a
                FROM
                    score
                WHERE
                    course_id = 1
            ) AS T1
        INNER JOIN (
            SELECT
                student_id,
                num AS b
            FROM
                score
            WHERE
                course_id = 2
        ) AS T2 ON T1.student_id = T2.student_id
        WHERE
            T1.a > T2.b
    ) AS B
LEFT JOIN student ON B.student_id = student.sid

10、查询有课程成绩小于60分的同学的学号、姓名；

 

方法一：表联合
SELECT
    B.student_id,
    student.sname
FROM
    (
        SELECT
            student_id
        FROM
            score
        WHERE
            num < 60
        GROUP BY
            student_id
    ) AS B
LEFT JOIN student ON B.student_id = student.sid

方法二：子查询
SELECT
    sid,
    sname
FROM
    student
WHERE
    sid IN (
        SELECT DISTINCT
            student_id
        FROM
            score
        WHERE
            num < 60
    )

11、查询没有学全所有课的同学的学号、姓名；

    思路：

        在分数表中根据学生进行分组，获取每一个学生选课数量

        如果数量 == 总课程数量，表示已经选择了所有课程

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id,
            COUNT(1) AS c
        FROM
            score
        GROUP BY
            student_id
        HAVING
            c = (SELECT count(1) FROM course)
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

12、查询至少有一门课与学号为“001”的同学所学相同的同学的学号和姓名；

    思路：

        获取 001 同学选择的所有课程

        获取课程在其中的所有人以及所有课程

        根据学生筛选，获取所有学生信息

        再与学生表连接，获取姓名

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id
        FROM
            score
        WHERE
            student_id != 1
        AND course_id IN (
            SELECT
                course_id
            FROM
                score
            WHERE
                student_id = 1
        )
        GROUP BY
            student_id
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

13、查询至少学过学号为“001”同学所有课的其他同学学号和姓名；

        先找到和001的学过的所有人

        然后个数 ＝ 001所有学科     ＝＝》 其他人可能选择的更多

SELECT
    score.student_id,
    student.sname,
    score.course_id,
    count(1) AS c
FROM
    score
LEFT JOIN student ON score.student_id = student.sid
WHERE
    student_id != 1
AND course_id IN (
    SELECT
        course_id
    FROM
        score
    WHERE
        student_id = 1
)
GROUP BY
    student_id
HAVING
    c = (
        SELECT
            COUNT(1)
        FROM
            score
        WHERE
            student_id = 1
    )

或者

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id,
            count(1) AS c
        FROM
            score
        WHERE
            student_id != 1 
                AND
            course_id IN (
                SELECT
                    course_id
                FROM
                    score
                WHERE
                    student_id = 1
            )
        GROUP BY
            student_id
        HAVING
            c = (
                SELECT
                    count(course_id)
                FROM
                    score
                WHERE
                    student_id = 1
            )
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；

         

        个数相同

        002学过的也学过

 

SELECT T.student_id,student.sname FROM
(
    SELECT student_id from score where student_id = 
        (
        SELECT student_id from score GROUP BY student_id 
        HAVING  count(1)= (SELECT count(1) from score where student_id = 2) and  student_id != 2
        ) 
    and course_id in (SELECT course_id from score where student_id = 2) 
    GROUP BY student_id 
    HAVING count(1) = (SELECT count(1) from score where student_id = 2)
) as T
LEFT JOIN student ON T.student_id = student.sid

15、删除学习“叶平”老师课的score表记录；

DELETE
FROM
    score
WHERE
    course_id IN (
        SELECT
            cid
        FROM
            teacher
        LEFT JOIN course ON teacher.tid = course.teacher_id
        WHERE
            tname = "李平老师"
    )

　　

16、向SC表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“002”课程的同学学号；②插入“002”号课程的平均成绩；

    思路：

        由于insert 支持 

                inset into tb1(xx,xx) select x1,x2 from tb2;

        所有，获取所有没上过002课的所有人，获取002的平均成绩

INSERT INTO score (student_id, course_id, num) SELECT
    student_id,
    2,
    (
        SELECT
            avg(num)
        FROM
            score
        WHERE
            course_id = 2
    )
FROM
    score
WHERE
    course_id != 2
GROUP BY
    student_id

17、按平均成绩从低到高 显示所有学生的“生物”、“物理”、“体育”三门的课程成绩，按如下形式显示： 学生ID,生物,物理,体育,有效课程数,有效平均分；

SELECT 
sc.student_id ,
    IFNULL(
   (SELECT num from score LEFT JOIN course ON 
    score.course_id = course.cid where cname = '生物' and sc.student_id = student_id)
    ,0) as 生物 ,
    IFNULL(
    (SELECT num FROM score LEFT JOIN course ON score.course_id = course.cid WHERE
cname = '物理' and sc.student_id = student_id)
    ,0) as 物理,
    IFNULL(
    (SELECT num FROM score LEFT JOIN course ON score.course_id = course.cid 
    where cname = '体育' and sc.student_id = student_id)
    ,0) as 体育,
    COUNT(sc.course_id),
    AVG(sc.num) as 平均分
FROM score as sc
GROUP BY sc.student_id
ORDER BY 平均分 ASC

18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，课程名称，最高分，最低分；

SELECT
    课程ID,
    course.cname AS 课程名称,
    最高分,
    最低分
FROM
    (
        SELECT
            course_id AS 课程ID,
            max(num) AS 最高分,
            min(num) AS 最低分
        FROM
            score
        GROUP BY
            course_id
    ) AS T
LEFT JOIN course ON T.课程ID = course.cid

19、按各科平均成绩从低到高和及格率的百分数从高到低顺序；

    思路：case when .. then

SELECT cname as 课程名,平均分,及格率 from 
(
SELECT course_id,AVG(num) as 平均分,sum(CASE WHEN num>=60 then 1 ELSE 0 END)/count(course_id)*100 as 及格率 from score GROUP BY course_id ORDER BY 平均分 ASC,及格率 DESC
 ) as T
LEFT JOIN course ON T.course_id = course.cid

 

20、课程平均分从高到低显示（现实任课老师）；

SELECT
    teacher.tname,
    平均分
FROM
    (
        SELECT
            course_id,
            avg(IFNULL(num, 0)) AS 平均分
        FROM
            score
        GROUP BY
            course_id
        ORDER BY
            平均分 DESC
    ) AS T
LEFT JOIN course ON T.course_id = course.cid
LEFT JOIN teacher ON course.teacher_id = teacher.tid

 21、查询各科成绩前三名的记录:(不考虑成绩并列情况)

 

SELECT  course_id,num from score  LEFT JOIN
(SELECT sid, 
(select num from score as s2 where course_id = s1.course_id ORDER BY num  desc LIMIT 0,1) as first,
(SELECT num FROM score as s2 where course_id = s1.course_id ORDER BY num desc LIMIT 2,1) as end
FROM score as s1
) as T
ON score.sid = T.sid
where score.num >= T.end and score.num <= T.first
order BY course_id asc,num desc

 

22、查询每门课程被选修的学生数；

SELECT
    course.cname AS 课程,
    人数
FROM
    (
        SELECT
            course_id,
            COUNT(1) AS 人数
        FROM
            score
        GROUP BY
            course_id
    ) AS T
LEFT JOIN course ON T.course_id = course.cid

23、查询出只选修了一门课程的全部学生的学号和姓名；

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id
        FROM
            score
        GROUP BY
            student_id
        HAVING
            COUNT(student_id) = 1
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

24、查询男生、女生的人数；

SELECT
    (
        SELECT
            COUNT(1)
        FROM
            student
        WHERE
            gender = '男'
    ) AS 男,
    (
        SELECT
            COUNT(1)
        FROM
            student
        WHERE
            gender = '女'
    ) AS 女

25、查询姓“张”的学生名单；

SELECT * from student where sname like "张%"

26、查询同名同姓学生名单，并统计同名人数；

SELECT
    sname,
    count(1) AS 同名人数
FROM
    student
GROUP BY
    sname
HAVING
    count(1) > 1

27、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；

SELECT
    course.cname AS 课程,
    平均成绩
FROM
    (
        SELECT
            course_id,
            AVG(num) AS 平均成绩
        FROM
            score
        GROUP BY
            course_id
        ORDER BY
            平均成绩 ASC,
            course_id DESC
    ) AS T
LEFT JOIN course ON T.course_id = course.cid

28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；

SELECT
    T.student_id AS 学号,
    student.sname AS 姓名,
    平均成绩
FROM
    (
        SELECT
            student_id,
            avg(num) AS 平均成绩
        FROM
            score
        GROUP BY
            student_id
        HAVING
            AVG(IFNULL(num, 0)) > 85
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

29、查询课程名称为“物理”，且分数低于60的学生姓名和分数；

SELECT
    student.sname AS 姓名,
    T.分数
FROM
    (
        SELECT
            student_id,
            num AS 分数
        FROM
            score
        LEFT JOIN course ON score.course_id = course.cid
        WHERE
            cname = "物理"
        AND num < 60
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；

SELECT
    T.student_id AS 学号,
    student.sname AS 姓名,
    T.分数
FROM
    (
        SELECT
            student_id,
            num AS 分数
        FROM
            score
        WHERE
            course_id = 3
        AND num > 80
    ) AS T
LEFT JOIN student ON T.student_id = student.sid

31、求选了课程的学生人数

SELECT  count(DISTINCT student_id) from score 

32、查询选修“张磊”老师所授课程的学生中，成绩最高的学生姓名及其成绩；

SELECT
    T.学号,
    student.sname AS 姓名,
    T.成绩
FROM
    (
        SELECT
            student_id AS 学号,
            num AS 成绩
        FROM
            score
        WHERE
            course_id IN (
                SELECT
                    cid
                FROM
                    teacher
                LEFT JOIN course ON tid = course.teacher_id
                WHERE
                    tname = '张磊老师'
            )
        ORDER BY
            num DESC
        LIMIT 1
    ) AS T
LEFT JOIN student ON T.学号 = student.sid

33、查询各个课程及相应的选修人数；

SELECT
    course.cname AS 课程,
    T.选修人数
FROM
    (
        SELECT
            course_id,
            COUNT(1) AS 选修人数
        FROM
            score
        GROUP BY
            course_id
    ) AS T
LEFT JOIN course ON T.course_id = course.cid

34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；

SELECT
    s1.student_id AS 学号,
    s1.course_id AS 课程1,
    s1.num AS 课程1得分,
    s2.course_id AS 课程2,
    s2.num AS 课程2得分
FROM
    score AS s1,
    score AS s2
WHERE
    s1.student_id = s2.student_id
AND s1.course_id != s2.course_id
AND s1.num = s2.num 

35、查询每门课程成绩最好的前两名；

SELECT course_id,score.num from score LEFT JOIN
(
select sid,num,
(select num from score where course_id = s1.course_id ORDER BY num desc LIMIT 2,1) as s2end
FROM score as s1
) as T ON score.sid = T.sid
where score.num >= T.s2end
order BY score.course_id asc,score.num DESC

36、检索至少选修两门课程的学生学号；

SELECT student_id FROM score GROUP BY student_id  HAVING count(1) > 1

37、查询全部学生都选修的课程的课程号和课程名；

SELECT course_id from score GROUP BY  course_id  HAVING count(1) = (SELECT COUNT(1) FROM student)

38、查询没学过“叶平”老师讲授的任一门课程的学生姓名；

SELECT
    T.student_id,
    student.sname
FROM
    (
        SELECT
            student_id
        FROM
            score
        WHERE
            course_id NOT IN (
                SELECT
                    cid
                FROM
                    teacher
                LEFT JOIN course ON teacher.tid = course.teacher_id
                WHERE
                    tname = '李平老师'
            )
        GROUP BY
            student_id
    ) AS T
LEFT JOIN student ON student.sid = T.student_id

39、查询两门或两门以上不及格课程的同学的学号及其平均成绩；

SELECT
    student_id,
    avg(num) AS 平均成绩
FROM
    score
GROUP BY
    student_id
HAVING
    sum(
        CASE
        WHEN num < 60 THEN
            1
        ELSE
            0
        END
    ) >= 2

40、检索“004”课程分数小于60，按分数降序排列的同学学号；

SELECT
    student_id,
    num
FROM
    score
WHERE
    course_id = 4
AND num < 60
ORDER BY
    num DESC

41、删除“002”同学的“001”课程的成绩；

delete from score where student_id = 2 and course_id = 1