MySQL练习题

表结构如图所示

 

/*
 Navicat Premium Data Transfer

 Source Server         : localhost
 Source Server Type    : MySQL
 Source Server Version : 50730
 Source Host           : localhost:3306
 Source Schema         : test

 Target Server Type    : MySQL
 Target Server Version : 50730
 File Encoding         : 65001

 Date: 12/08/2020 21:26:48
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for class
-- ----------------------------
DROP TABLE IF EXISTS `class`;
CREATE TABLE `class`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 6 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of class
-- ----------------------------
INSERT INTO `class` VALUES (1, '高三1班');
INSERT INTO `class` VALUES (2, '高三2班');
INSERT INTO `class` VALUES (3, '高三3班');
INSERT INTO `class` VALUES (4, '高三4班');
INSERT INTO `class` VALUES (5, '高三5班');

-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `subject` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `teacherid` int(11) NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `fk_course_teacher`(`teacherid`) USING BTREE,
  CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacherid`) REFERENCES `teacher` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES (1, '语文', 3);
INSERT INTO `course` VALUES (2, '数学', 1);
INSERT INTO `course` VALUES (3, '英语', 5);
INSERT INTO `course` VALUES (4, '物理', 4);
INSERT INTO `course` VALUES (5, '生物', 3);
INSERT INTO `course` VALUES (6, '化学', 2);

-- ----------------------------
-- Table structure for score
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `studentid` int(11) NOT NULL,
  `courseid` int(11) NOT NULL,
  `grade` int(11) NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `fk_score_student`(`studentid`) USING BTREE,
  INDEX `fk_score_course`(`courseid`) USING BTREE,
  CONSTRAINT `fk_score_course` FOREIGN KEY (`courseid`) REFERENCES `course` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT,
  CONSTRAINT `fk_score_student` FOREIGN KEY (`studentid`) REFERENCES `student` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB AUTO_INCREMENT = 59 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES (1, 1, 5, 30);
INSERT INTO `score` VALUES (2, 1, 4, 40);
INSERT INTO `score` VALUES (3, 1, 1, 25);
INSERT INTO `score` VALUES (4, 1, 3, 68);
INSERT INTO `score` VALUES (5, 2, 4, 66);
INSERT INTO `score` VALUES (6, 2, 1, 35);
INSERT INTO `score` VALUES (7, 3, 6, 65);
INSERT INTO `score` VALUES (8, 3, 3, 68);
INSERT INTO `score` VALUES (9, 3, 5, 64);
INSERT INTO `score` VALUES (10, 4, 1, 77);
INSERT INTO `score` VALUES (11, 4, 6, 66);
INSERT INTO `score` VALUES (12, 4, 3, 87);
INSERT INTO `score` VALUES (13, 4, 4, 99);
INSERT INTO `score` VALUES (14, 4, 2, 79);
INSERT INTO `score` VALUES (15, 5, 2, 45);
INSERT INTO `score` VALUES (16, 5, 3, 67);
INSERT INTO `score` VALUES (17, 6, 4, 82);
INSERT INTO `score` VALUES (18, 6, 1, 79);
INSERT INTO `score` VALUES (19, 6, 2, 29);
INSERT INTO `score` VALUES (20, 7, 3, 67);
INSERT INTO `score` VALUES (21, 7, 4, 100);
INSERT INTO `score` VALUES (22, 8, 1, 37);
INSERT INTO `score` VALUES (23, 8, 2, 98);
INSERT INTO `score` VALUES (24, 8, 3, 67);
INSERT INTO `score` VALUES (25, 9, 4, 89);
INSERT INTO `score` VALUES (26, 9, 1, 56);
INSERT INTO `score` VALUES (27, 10, 2, 77);
INSERT INTO `score` VALUES (28, 11, 3, 67);
INSERT INTO `score` VALUES (29, 11, 2, 88);
INSERT INTO `score` VALUES (30, 10, 6, 41);
INSERT INTO `score` VALUES (31, 12, 2, 100);
INSERT INTO `score` VALUES (32, 14, 3, 67);
INSERT INTO `score` VALUES (33, 16, 4, 88);
INSERT INTO `score` VALUES (34, 10, 5, 91);
INSERT INTO `score` VALUES (35, 20, 2, 88);
INSERT INTO `score` VALUES (36, 15, 3, 67);
INSERT INTO `score` VALUES (37, 11, 4, 22);
INSERT INTO `score` VALUES (38, 10, 1, 82);
INSERT INTO `score` VALUES (39, 10, 3, 77);
INSERT INTO `score` VALUES (40, 14, 1, 43);
INSERT INTO `score` VALUES (41, 16, 4, 87);
INSERT INTO `score` VALUES (42, 13, 1, 93);
INSERT INTO `score` VALUES (43, 17, 2, 77);
INSERT INTO `score` VALUES (44, 19, 3, 43);
INSERT INTO `score` VALUES (45, 20, 4, 87);
INSERT INTO `score` VALUES (46, 16, 1, 90);
INSERT INTO `score` VALUES (47, 18, 2, 77);
INSERT INTO `score` VALUES (48, 13, 3, 43);
INSERT INTO `score` VALUES (49, 12, 6, 73);
INSERT INTO `score` VALUES (50, 14, 5, 87);
INSERT INTO `score` VALUES (51, 14, 3, 60);
INSERT INTO `score` VALUES (52, 12, 3, 100);
INSERT INTO `score` VALUES (53, 7, 5, 67);
INSERT INTO `score` VALUES (54, 4, 5, 50);
INSERT INTO `score` VALUES (55, 8, 6, 80);
INSERT INTO `score` VALUES (56, 8, 5, 70);
INSERT INTO `score` VALUES (57, 8, 4, 75);
INSERT INTO `score` VALUES (58, 10, 4, 86);

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `gender` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  `class_id` int(11) NOT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `fk_class`(`class_id`) USING BTREE,
  CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`id`) ON DELETE RESTRICT ON UPDATE RESTRICT
) ENGINE = InnoDB AUTO_INCREMENT = 21 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '张瑞政', '男', 1);
INSERT INTO `student` VALUES (2, '杨思琦', '女', 2);
INSERT INTO `student` VALUES (3, '郑大同', '男', 4);
INSERT INTO `student` VALUES (4, '何香凝', '女', 3);
INSERT INTO `student` VALUES (5, '李嘉欣', '男', 2);
INSERT INTO `student` VALUES (6, '邓丽欣', '男', 1);
INSERT INTO `student` VALUES (7, '张雨绮', '女', 3);
INSERT INTO `student` VALUES (8, '张素晗', '男', 1);
INSERT INTO `student` VALUES (9, '张云川', '男', 4);
INSERT INTO `student` VALUES (10, '何其芳', '女', 2);
INSERT INTO `student` VALUES (11, '许本谦', '男', 1);
INSERT INTO `student` VALUES (12, '何家产', '男', 3);
INSERT INTO `student` VALUES (13, '马季', '男', 2);
INSERT INTO `student` VALUES (14, '李心洁', '女', 4);
INSERT INTO `student` VALUES (15, '许椿生', '男', 3);
INSERT INTO `student` VALUES (16, '马朴', '男', 2);
INSERT INTO `student` VALUES (17, '何休', '男', 1);
INSERT INTO `student` VALUES (18, '吴西', '女', 4);
INSERT INTO `student` VALUES (19, '邓丽欣', '女', 3);
INSERT INTO `student` VALUES (20, '杨采妮', '女', 4);

-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 6 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES (1, '蔡文浩老师');
INSERT INTO `teacher` VALUES (2, '宋洁涵老师');
INSERT INTO `teacher` VALUES (3, '唐诗咏老师');
INSERT INTO `teacher` VALUES (4, '余景生老师');
INSERT INTO `teacher` VALUES (5, '冯英子老师');

SET FOREIGN_KEY_CHECKS = 1;

练习题及答案（使用Navicat操作）

#表course中老师任课的课数是多少
select teacherid,count(1) from course group by teacherid;


#表student中男女个数分别是多少
select gender,count(id) from student group by gender;


#临时表操作
select studentid,grade from (select * from score where grade>60) as B;


#查询平均成绩大于60分的同学的"学号"和"平均成绩"
select studentid,avg(grade) from score group by studentid having avg(grade)>60;


#查询平均成绩大于60分的同学的"名字"和"平均成绩"
SELECT student.name "姓名", AVG(grade) "平均成绩" FROM score INNER JOIN student ON student.id=score.studentid GROUP BY studentid HAVING AVG(grade)>60;


#查询所有同学的学号、姓名、选课数、总成绩
SELECT studentid "学号", student.name "姓名", COUNT(1) "选课数", SUM(grade) "总成绩" FROM score INNER JOIN student ON student.id=score.studentid GROUP BY studentid;


#查询没学过"冯英子"老师的课的同学的学号、姓名
    "冯英子"老师任教的课程的id
    select course.id from course left join teacher on course.teacherid=teacher.id where teacher.name = "冯英子老师"

    学过"冯英子"老师的课的所有同学的id
    select studentid from score where courseid in 
    (select course.id from course left join teacher on course.teacherid=teacher.id where teacher.name = "冯英子老师") 
    group by studentid;

    最终结果
    select student.id,student.name from student where id not in
    (select studentid from score where courseid in 
    (select course.id from course left join teacher on course.teacherid=teacher.id where teacher.name = "冯英子老师") 
    group by studentid);


#查询"生物"课程比"物理"课程成绩低的所有学生的学号
select A.studentid from
(select score.studentid,course.subject,score.grade from score left join course on score.courseid=course.id where course.subject="生物") as A
inner join
(select score.studentid,course.subject,score.grade from score left join course on score.courseid=course.id where course.subject="物理") as B
on A.studentid=B.studentid where A.grade<B.grade;


#查询学过编号"1"并且也学过编号"2"课程的同学的学号、姓名
select score.studentid,student.name from score 
left join student on score.studentid=student.id
where score.courseid=1 or score.courseid=2 
group by score.studentid having count(1)>1;


#查询学过"唐诗咏"老师所教的所有课的同学的学号、姓名
select studentid from score where courseid in
(select course.id from course
left join teacher on course.teacherid=teacher.id 
where teacher.name="唐诗咏老师")
group by studentid 
having count(courseid)=(
select count(1) from course
left join teacher on course.teacherid=teacher.id 
where teacher.name="唐诗咏老师")


#查询学过"唐诗咏"老师所教的所有课的同学的学号、姓名
select student.id,student.name from
(select studentid from score where courseid in
(select course.id from course
left join teacher on course.teacherid=teacher.id 
where teacher.name="唐诗咏老师")
group by studentid 
having count(courseid)=(
select count(1) from course
left join teacher on course.teacherid=teacher.id 
where teacher.name="唐诗咏老师")) as B
left join student on B.studentid=student.id;


#查询没有学全所有课的同学的学号、姓名
select student.id,student.name from 
(select studentid,count(id) from score group by studentid
having count(id)<(select count(id) from course)) as B
left join student on B.studentid=student.id;


#查询至少有一门课与学号为"3"的同学所学相同的同学的学号和姓名

  SELECT sc.studentid,st.name FROM score sc INNER JOIN
  student st
  ON sc.studentid=st.id WHERE sc.courseid in
  (SELECT sc.courseid FROM score sc WHERE sc.studentid=3) AND st.id!=3 GROUP BY st.id;

#查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
select courseid,max(grade),min(grade) from score group by courseid;


#查询各科成绩最高和最低的分（如果分数小于30则显示0）：以如下形式显示：课程ID，最高分，最低分

  SELECT sc.courseid "课程ID", CASE
  WHEN MAX(sc.grade)<30 THEN
  0
  ELSE
  MAX(sc.grade)
  END "最高分",
  CASE
  WHEN MIN(sc.grade)<30 THEN
  0
  ELSE
  MIN(sc.grade)
  END "最低分" FROM score sc GROUP BY sc.courseid;

#按各科平均成绩从低到高排序及其及格率为多少
    步骤1
    select studentid,courseid,grade,case when grade<60 then 0 else 1 end from score;
    步骤2
    select studentid,courseid,grade,case when grade<60 then 0 else 1 end,1 from score;
    步骤3
    select courseid,avg(grade),sum(case when grade<60 then 0 else 1 end),sum(1) from score group by score.courseid;
    最终结果：

select courseid "课程id",
avg(grade) "平均成绩",
sum(case when grade<60 then 0 else 1 end)/sum(1) "及格率"
from score group by score.courseid order by avg(grade) asc;

#课程平均分从高到低显示（显示任课老师）

SELECT te.name "任课老师", AVG(sc.grade) "平均成绩" FROM score sc INNER JOIN course co ON sc.courseid=co.id
INNER JOIN teacher te ON co.teacherid=te.id
GROUP BY sc.courseid ORDER BY AVG(sc.grade) DESC;

#查询每门课程成绩最好的前两名

SELECT a.* FROM score a WHERE 2 >
(SELECT COUNT(1) FROM score b
WHERE a.courseid=b.courseid AND b.grade>a.grade)
ORDER BY courseid, grade DESC;

#查询每门课程被选修的学生数
select courseid,count(1) from score group by courseid;


#查询课程名称为"数学"，且分数低于60的学生姓名和分数

SELECT st.name "姓名", sc.grade "分数" FROM score sc
INNER JOIN student st ON sc.studentid=st.id
INNER JOIN course co ON sc.courseid=co.id
WHERE sc.grade<60 AND co.subject="数学";