46-sql语句练习

init.sql文件内容

/*
 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;

cmd导入init.sql文件：

mysql> create database db1;
mysql> use db1;
mysql> source /root/init.sql

练习：

1、查询所有的课程的名称以及对应的任课老师姓名

SELECT
    cname,
    tname 
FROM
    course
    LEFT JOIN teacher ON teacher_id = tid;

2、查询学生表中男女生各有多少人

SELECT
    gender 性别,
    count( 1 ) 人数 
FROM
    student 
GROUP BY
    gender;

3、查询物理成绩等于100的学生的姓名

SELECT
    sname 
FROM
    student 
WHERE
    sid IN (
SELECT
    student_id 
FROM
    score
    INNER JOIN course ON score.course_id = course.cid 
WHERE
    course.cname = "物理" 
    AND score.num = 100 
    );

4、查询平均成绩大于八十分的同学的姓名和平均成绩

SELECT
    student.sname,
    t1.avg_num 
FROM
    student
    INNER JOIN ( SELECT student_id, avg( num ) AS avg_num FROM score GROUP BY student_id HAVING avg( num ) > 80 ) AS t1 ON student.sid = t1.student_id;

5、查询所有学生的学号，姓名，选课数，总成绩

SELECT
    student.sid,
    student.sname,
    t1.course_sum,
    t1.total_num 
FROM
    student
    LEFT JOIN ( SELECT student_id, count( course_id ) course_sum, sum( num ) total_num FROM score GROUP BY student_id ) AS t1 ON student.sid = t1.student_id;

6、 查询姓李老师的个数

select count(tid) from teacher where tname like "李%";

7、 查询没有报李平老师课的学生姓名

SELECT
    sname 
FROM
    student 
WHERE
    sid NOT IN (
SELECT DISTINCT
    student_id 
FROM
    score 
WHERE
    course_id IN ( SELECT course.cid FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid WHERE teacher.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
    t1.student_id 
FROM
    ( SELECT student_id, num FROM score WHERE course_id = ( SELECT cid FROM course WHERE cname = "物理" ) ) AS t1
    INNER JOIN ( SELECT student_id, num FROM score WHERE course_id = ( SELECT cid FROM course WHERE cname = "生物" ) ) AS t2 ON t1.student_id = t2.student_id 
WHERE
    t1.num > t2.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
    student.sname 
FROM
    student 
WHERE
    sid IN (
SELECT
    student_id 
FROM
    score 
WHERE
    course_id IN ( SELECT cid FROM course WHERE cname = "物理" OR "体育" ) 
GROUP BY
    student_id 
HAVING
    count( course_id ) = 1 
    );

10、查询挂科超过两门(包括两门)的学生姓名和班级

SELECT
    student.sname,
    class.caption 
FROM
    student
    INNER JOIN ( SELECT student_id FROM score WHERE num < 60 GROUP BY student_id HAVING count( course_id ) >= 2 ) AS t1
    INNER JOIN class ON student.sid = t1.student_id 
    AND student.class_id = class.cid;

11 、查询选修了所有课程的学生姓名

SELECT
    student.sname 
FROM
    student 
WHERE
    sid IN ( SELECT student_id FROM score GROUP BY student_id HAVING count( course_id ) = ( SELECT count( cname ) FROM course ) );

12、查询李平老师教的课程的所有成绩记录

SELECT
    * 
FROM
    score 
WHERE
    course_id IN ( SELECT course.cid FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid WHERE teacher.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
    cid,
    cname 
FROM
    course 
WHERE
    cid IN ( SELECT course_id FROM score GROUP BY course_id HAVING count( student_id ) = ( SELECT count( sid ) FROM student ) );

14、查询每门课程被选修的次数

select course_id,count(student_id) from score group by course_id;

15、查询只选修了一门课程的学生姓名和学号

SELECT
    sid,
    sname 
FROM
    student 
WHERE
    sid IN ( SELECT student_id FROM score GROUP BY student_id HAVING count( course_id ) = 1 );

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 order by num desc;

17、查询平均成绩大于85的学生姓名和平均成绩

SELECT
    sname,
    t1.avg_num 
FROM
    student
    INNER JOIN ( SELECT student_id, avg( num ) avg_num FROM score GROUP BY student_id HAVING avg( num ) > 85 ) AS t1 ON student.sid = t1.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
    sname NAME,
    num 
FROM
    score
    LEFT JOIN course ON score.course_id = course.cid
    LEFT JOIN student ON score.student_id = student.sid 
WHERE
    course.cname = "生物" 
    AND score.num < 60;

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
            student_id
        FROM
            score
        WHERE
            course_id IN (
                SELECT
                    course.cid
                FROM
                    course
                INNER JOIN teacher ON course.teacher_id = teacher.tid
                WHERE
                    teacher.tname = '李平老师'
            )
        GROUP BY
            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
    *
FROM
    score
ORDER BY
    course_id,
    num DESC;