Mysql_多表查询练习

　　下面是数据初始化，在本地创建sql文件，拷贝代码内容，创建数据库，然后在数据库里source执行sql文件。

/*
 数据导入：
 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;

　　

　　题目如下：

1、查询所有的课程的名称以及对应的任课老师姓名

2、查询学生表中男女生各有多少人

3、查询物理成绩等于100的学生的姓名

4、查询平均成绩大于八十分的同学的姓名和平均成绩

5、查询所有学生的学号，姓名，选课数，总成绩

6、 查询姓李老师的个数

7、 查询没有报李平老师课的学生姓名

8、 查询物理课程比生物课程高的学生的学号

9、 查询没有同时选修物理课程和体育课程的学生姓名

10、查询挂科超过两门(包括两门)的学生姓名和班级
、查询选修了所有课程的学生姓名

12、查询李平老师教的课程的所有成绩记录

13、查询全部学生都选修了的课程号和课程名

14、查询每门课程被选修的次数

15、查询之选修了一门课程的学生姓名和学号

16、查询所有学生考出的成绩并按从高到低排序（成绩去重）

17、查询平均成绩大于85的学生姓名和平均成绩

18、查询生物成绩不及格的学生姓名和对应生物分数

19、查询在所有选修了李平老师课程的学生中，这些课程(李平老师的课程，不是所有课程)平均成绩最高的学生姓名

20、查询每门课程成绩最好的前两名学生姓名

21、查询不同课程但成绩相同的学号，课程号，成绩

22、查询没学过“叶平”老师课程的学生姓名以及选修的课程名称；

23、查询所有选修了学号为1的同学选修过的一门或者多门课程的同学学号和姓名；

24、任课最多的老师中学生单科成绩最高的学生姓名

　　答案：

-- 1、查询所有的课程的名称以及对应的任课老师姓名
SELECT
    c.cname,
    t.tname
FROM
    course c
LEFT JOIN teacher t ON c.teacher_id = t.tid;

-- 2、查询学生表中男女生各有多少人
SELECT
    gender,
    count(sid)count
FROM
    student
GROUP BY
    gender;

-- 3、查询物理成绩等于100的学生的姓名
SELECT
    a.sid,
    b.sname
FROM
    score a
LEFT JOIN student b ON a.student_id = b.sid
WHERE
    a.num = 100
AND a.course_id =(
    SELECT
        c.cid
    FROM
        course c
    WHERE
        c.cname = "物理"
);

-- 4、查询平均成绩大于八十分的同学的姓名和平均成绩
SELECT
    a.sname,
    c.avg_score
FROM
    student a
INNER JOIN(
    SELECT
        b.*, AVG(b.num)avg_score
    FROM
        score b
    GROUP BY
        b.student_id
    HAVING
        avg_score > 80
)c ON a.sid = c.student_id;

-- 5、查询所有学生的学号，姓名，选课数，总成绩
SELECT
    a.sid,
    a.sname,
    c.count_course,
    c.sum_score
FROM
    student a
LEFT JOIN(
    SELECT
        b.student_id,
        count(b.course_id)count_course,
        SUM(b.num)sum_score
    FROM
        score b
    GROUP BY
        b.student_id
)c ON a.sid = c.student_id;

-- 6、 查询姓李老师的个数
SELECT
    count(tid)
FROM
    teacher t
WHERE
    t.tname LIKE "李%";

-- 7、 查询没有报李平老师课的学生姓名
SELECT
    a.sname
FROM
    student a
WHERE
    a.sid NOT IN(
        SELECT
            b.student_id
        FROM
            score b
        WHERE
            course_id IN(
                SELECT
                    c.cid
                FROM
                    course c
                WHERE
                    c.teacher_id IN(
                        SELECT
                            d.tid
                        FROM
                            teacher d
                        WHERE
                            d.tname = "李平老师"
                    )
            )
    );

-- 8、 查询物理课程比生物课程高的学生的学号
SELECT
    c.student_id
FROM
    (
        SELECT
            *
        FROM
            score a
        WHERE
            a.course_id =(
                SELECT
                    b.cid
                FROM
                    course b
                WHERE
                    b.cname = "物理"
            )
    )c
INNER JOIN(
    SELECT
        *
    FROM
        score d
    WHERE
        d.course_id =(
            SELECT
                f.cid
            FROM
                course f
            WHERE
                f.cname = "生物"
        )
)g ON c.student_id = g.student_id
AND c.num > g.num;

-- 9、 查询没有同时选修物理课程和体育课程的学生姓名
SELECT
    a.sname
FROM
    student a
WHERE
    a.sid NOT IN(
        SELECT
            d.student_id
        FROM
            (
                SELECT
                    *
                FROM
                    score b
                WHERE
                    b.course_id =(
                        SELECT
                            c.cid
                        FROM
                            course c
                        WHERE
                            c.cname = "物理"
                    )
            )d
        INNER JOIN(
            SELECT
                *
            FROM
                score f
            WHERE
                f.course_id =(
                    SELECT
                        g.cid
                    FROM
                        course g
                    WHERE
                        g.cname = "体育"
                )
        )h ON d.student_id = h.student_id
    );

-- 10、查询挂科超过两门(包括两门)的学生姓名和班级
SELECT
    c.sname,
    c.caption
FROM
    (
        SELECT
            *
        FROM
            student a
        LEFT JOIN class b ON a.class_id = b.cid
    )c
INNER JOIN(
    SELECT
        d.student_id,
        count(d.student_id)count
    FROM
        score d
    WHERE
        d.num < 60
    GROUP BY
        d.student_id
    HAVING
        count >= 2
)e ON c.sid = e.student_id;

-- 11、查询选修了所有课程的学生姓名
SELECT
    s.sname
FROM
    student s
INNER JOIN(
    SELECT
        a.student_id,
        count(a.course_id)count_course
    FROM
        score a
    GROUP BY
        a.student_id
    HAVING
        count_course =(SELECT count(*) FROM course)
)b ON s.sid = b.student_id;

-- 12、查询李平老师教的课程的所有成绩记录
SELECT
    a.*
FROM
    score a
WHERE
    a.course_id IN(
        SELECT
            b.cid
        FROM
            course b
        WHERE
            b.teacher_id =(
                SELECT
                    c.tid
                FROM
                    teacher c
                WHERE
                    c.tname = "李平老师"
            )
    )

-- 13、查询全部学生都选修了的课程号和课程名
    SELECT
        c.cid,
        c.cname
    FROM
        course c
    INNER JOIN(
        SELECT
            a.course_id,
            count(a.student_id)count_student
        FROM
            score a
        GROUP BY
            a.course_id
        HAVING
            count_student =(SELECT count(*) FROM student)
    )b ON c.cid = b.course_id;

-- 14、查询每门课程被选修的次数
SELECT
    c.cid,
    c.cname,
    b.count_student
FROM
    course c
LEFT JOIN(
    SELECT
        a.course_id,
        count(a.student_id)count_student
    FROM
        score a
    GROUP BY
        a.course_id
)b ON c.cid = b.course_id;

-- 15、查询只选修了一门课程的学生姓名和学号
SELECT
    s.sname
FROM
    student s
INNER JOIN(
    SELECT
        a.student_id,
        count(a.course_id)count_course
    FROM
        score a
    GROUP BY
        a.student_id
    HAVING
        count_course = 1
)b ON s.sid = b.student_id;

-- 16、查询所有学生考出的成绩并按从高到低排序（成绩去重）
SELECT DISTINCT
    (num)
FROM
    score a
ORDER BY
    a.num DESC 

-- 17、查询平均成绩大于85的学生姓名和平均成绩
    SELECT
        a.sname
    FROM
        student a
    INNER JOIN(
        SELECT
            b.student_id,
            avg(b.num)avg_num
        FROM
            score b
        GROUP BY
            b.student_id
        HAVING
            avg_num > 85
    )c ON a.sid = c.student_id;

-- 18、查询生物成绩不及格的学生姓名和对应生物分数
SELECT
    a.sname,
    c.num
FROM
    student a
INNER JOIN(
    SELECT
        b.student_id,
        b.num
    FROM
        score b
    WHERE
        b.course_id =(
            SELECT
                cid
            FROM
                course
            WHERE
                cname = "生物"
        )
    AND b.num < 60
)c ON a.sid = c.student_id;

-- 19、查询在所有选修了李平老师课程的学生中，这些课程(李平老师的课程，不是所有课程)平均成绩最高的学生姓名
SELECT
    sname
FROM
    student
WHERE
    sid =(
        SELECT
            a.student_id
        FROM
            score a
        WHERE
            a.course_id IN(
                SELECT
                    b.cid
                FROM
                    course b
                WHERE
                    b.teacher_id =(
                        SELECT
                            c.tid
                        FROM
                            teacher c
                        WHERE
                            c.tname = "李平老师"
                    )
            )
        GROUP BY
            a.student_id
        ORDER BY
            avg(num)DESC
        LIMIT 1
    )

-- 20、查询每门课程成绩最好的前两名学生姓名
    SELECT
        e.sname,
        f.course_id,
        f.num
    FROM
        student e
    INNER JOIN(
        SELECT
            c.*
        FROM
            score c
        INNER JOIN(
            SELECT
                *
            FROM
                (
                    SELECT
                        course_id,
                        MAX(num)num
                    FROM
                        score
                    GROUP BY
                        course_id
                    ORDER BY
                        course_id,
                        num DESC
                )a
            UNION ALL
                (
                    SELECT
                        a.course_id,
                        MAX(a.num)num
                    FROM
                        score a
                    INNER JOIN(
                        SELECT
                            course_id,
                            MAX(num)num
                        FROM
                            score
                        GROUP BY
                            course_id
                        ORDER BY
                            course_id,
                            num DESC
                    )b ON a.course_id = b.course_id
                    WHERE
                        a.num < b.num
                    GROUP BY
                        a.course_id
                )
        )d ON c.course_id = d.course_id
        WHERE
            c.num = d.num
        ORDER BY
            c.course_id,
            c.num DESC
    )f ON e.sid = f.student_id
    ORDER BY
        f.course_id,
        f.num DESC 

-- 21、查询不同课程但成绩相同的学号，课程号，成绩
        SELECT
            student_id,
            course_id,
            num
        FROM
            score
        WHERE
            num IN(
                SELECT
                    a.num
                FROM
                    (
                        SELECT
                            *
                        FROM
                            score
                        GROUP BY
                            course_id,
                            num
                    )a
                GROUP BY
                    a.num
                HAVING
                    count(a.num)> 1
            )
        ORDER BY
            num;

-- 22、查询没学过“叶平”老师课程的学生姓名以及选修的课程名称；
SELECT
    c.sname,
    GROUP_CONCAT(d.cname)
FROM
    (
        SELECT
            a.*, b.course_id
        FROM
            (
                SELECT
                    *
                FROM
                    student
                WHERE
                    sid NOT IN(
                        SELECT DISTINCT
                            (student_id)
                        FROM
                            score
                        WHERE
                            course_id IN(
                                SELECT
                                    cid
                                FROM
                                    course
                                WHERE
                                    teacher_id =(
                                        SELECT
                                            tid
                                        FROM
                                            teacher
                                        WHERE
                                            tname = "李平老师"
                                    )
                            )
                    )
            )a
        INNER JOIN score b ON a.sid = b.student_id
    )c
INNER JOIN course d ON c.course_id = d.cid
GROUP BY
    c.sname 

-- 23、查询所有选修了学号为1的同学选修过的一门或者多门课程的同学学号和姓名；
    SELECT
        a.sid,
        a.sname
    FROM
        student a
    INNER JOIN(
        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
    )b ON a.sid = b.student_id 

-- 24、任课最多的老师中学生单科成绩最高的学生姓名
    SELECT
        sname
    FROM
        student
    WHERE
        sid =(
            SELECT
                student_id
            FROM
                score
            WHERE
                course_id IN(
                    SELECT
                        cid
                    FROM
                        course
                    WHERE
                        teacher_id =(
                            SELECT
                                teacher_id
                            FROM
                                course
                            GROUP BY
                                teacher_id
                            ORDER BY
                                count(teacher_id)DESC
                            LIMIT 1
                        )
                )
            ORDER BY
                num DESC
            LIMIT 1
        )