mysql 练习

1.导入导出

　　mysqldump -uroot -proot dbschool >C:\Users\Administrator\Desktop\123.sql      #结构 +数据

　　mysqldump -uroot -proot -d dbschool >C:\Users\Administrator\Desktop\456.sql   #仅仅导出表结构

　　

　　mysqldump -uroot -proot dbschool < C:\Users\Administrator\Desktop\123.sql   #导入时，要数据库名保持一致

2.根据表创建数据库

-- MySQL dump 10.13  Distrib 5.7.18, for Win64 (x86_64)
--
-- Host: localhost    Database: dbschool
-- ------------------------------------------------------
-- Server version    5.7.18

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE='+00:00' */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

--
-- Table structure for table `class`
--

DROP TABLE IF EXISTS `class`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `class` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `caption` char(4) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `class`
--

LOCK TABLES `class` WRITE;
/*!40000 ALTER TABLE `class` DISABLE KEYS */;
INSERT INTO `class` VALUES (1,'三年一班'),(2,'三年二班'),(3,'三年三班'),(4,'三年四班');
/*!40000 ALTER TABLE `class` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `course`
--

DROP TABLE IF EXISTS `course`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `course` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `cname` char(5) DEFAULT NULL,
  `teach_id` int(11) NOT NULL,
  PRIMARY KEY (`cid`),
  KEY `teach_id` (`teach_id`),
  CONSTRAINT `course_ibfk_1` FOREIGN KEY (`teach_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `course`
--

LOCK TABLES `course` WRITE;
/*!40000 ALTER TABLE `course` DISABLE KEYS */;
INSERT INTO `course` VALUES (1,'美术',1),(2,'数学',2),(3,'语文',3);
/*!40000 ALTER TABLE `course` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `score`
--

DROP TABLE IF EXISTS `score`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `score` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) NOT NULL,
  `course_id` int(11) NOT NULL,
  `number` int(3) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `student_id` (`student_id`),
  KEY `course_id` (`course_id`),
  CONSTRAINT `score_ibfk_1` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`),
  CONSTRAINT `score_ibfk_2` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `score`
--

LOCK TABLES `score` WRITE;
/*!40000 ALTER TABLE `score` DISABLE KEYS */;
INSERT INTO `score` VALUES (1,1,1,60),(2,1,2,80),(3,1,3,100),(4,2,1,70),(5,2,2,90),(6,2,3,60),(7,5,1,30),(8,5,2,50),(9,5,3,40),(10,7,1,80),(11,7,2,80),(12,7,3,80);
/*!40000 ALTER TABLE `score` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `student`
--

DROP TABLE IF EXISTS `student`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `student` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `sname` char(5) DEFAULT NULL,
  `gender` char(2) DEFAULT NULL,
  `class_id` int(11) NOT NULL,
  PRIMARY KEY (`sid`),
  KEY `class_id` (`class_id`),
  CONSTRAINT `student_ibfk_1` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `student`
--

LOCK TABLES `student` WRITE;
/*!40000 ALTER TABLE `student` DISABLE KEYS */;
INSERT INTO `student` VALUES (1,'张一','男',1),(2,'李一','男',1),(3,'王一','女',1),(4,'赵一','女',1),(5,'张二','男',2),(6,'李二','男',2),(7,'王二','女',2),(8,'赵二','女',2),(9,'张三','男',3),(10,'李三','男',3),(11,'王三','女',3),(12,'赵三','女',3),(13,'张四','男',4),(14,'李四','男',4),(15,'王四','女',4),(16,'赵四','女',4);
/*!40000 ALTER TABLE `student` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `teacher`
--

DROP TABLE IF EXISTS `teacher`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` char(5) DEFAULT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `teacher`
--

LOCK TABLES `teacher` WRITE;
/*!40000 ALTER TABLE `teacher` DISABLE KEYS */;
INSERT INTO `teacher` VALUES (1,'齐白石'),(2,'祖冲之'),(3,'鲁迅');
/*!40000 ALTER TABLE `teacher` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

-- Dump completed on 2017-06-11 14:07:55

3.练习

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；
思路：
    获取所有有生物课程的人（学号，成绩） - 临时表
    获取所有有物理课程的人（学号，成绩） - 临时表
    根据【学号】连接两个临时表：
        学号  物理成绩   生物成绩
 
    然后再进行筛选
 
        select A.student_id,sw,ty from
 
        (select student_id,num as sw from score left join course on score.course_id = course.cid where course.cname = '生物') as A
 
        left join
 
        (select student_id,num  as ty from score left join course on score.course_id = course.cid where course.cname = '体育') as B
 
        on A.student_id = B.student_id where sw > if(isnull(ty),0,ty);
 
3、查询平均成绩大于60分的同学的学号和平均成绩；
    思路：
        根据学生分组，使用avg获取平均值，通过having对avg进行筛选
 
        select student_id,avg(num) from score group by student_id having avg(num) > 60
 
4、查询所有同学的学号、姓名、选课数、总成绩；
 
    select score.student_id,sum(score.num),count(score.student_id),student.sname
    from
        score left join student on score.student_id = student.sid  
    group by score.student_id
 
5、查询姓“李”的老师的个数；
    select count(tid) from teacher where tname like '李%'
 
    select count(1) from (select tid from teacher where tname like '李%') as B
 
6、查询没学过“叶平”老师课的同学的学号、姓名；
    思路：
        先查到“李平老师”老师教的所有课ID
        获取选过课的所有学生ID
        学生表中筛选
    select * from student where sid not in (
        select DISTINCT student_id from score where score.course_id in (
            select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '李平老师'
        )
    )
 
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 student_id,sname from
 
    (select student_id,course_id from score where course_id = 1 or course_id = 2) as B
      
    left join student on B.student_id = student.sid group by student_id HAVING count(student_id) > 1
 
 
8、查询学过“叶平”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)
 
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
 
 
10、查询有课程成绩小于60分的同学的学号、姓名；
         
    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 student_id,sname
        from score left join student on score.student_id = student.sid
        group by student_id HAVING count(course_id) = (select count(1) from course)
 
 
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 student_id,sname, count(course_id)
        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
 
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 student_id,sname, count(course_id)
        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 count(course_id) ＝ (select count(course_id) from score where student_id = 1)
 
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 student_id,sname from score left join student on score.student_id = student.sid where student_id in (
            select student_id from score  where student_id != 1 group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
        ) and course_id in (select course_id from score where student_id = 1) group by student_id HAVING count(course_id) = (select count(1) from score where student_id = 1)
 
 
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 course left join teacher on course.teacher_id = teacher.tid where teacher.name = '叶平'
    )
 
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 sid,2,(select avg(num) from score where course_id = 2)
    from student where sid not in (
        select student_id from score where course_id = 2
    )
     
17、按平均成绩从低到高 显示所有学生的“语文”、“数学”、“英语”三门的课程成绩，按如下形式显示： 学生ID,语文,数学,英语,有效课程数,有效平均分；
    select sc.student_id,
        (select num from score left join course on score.course_id = course.cid where course.cname = "生物" and score.student_id=sc.student_id) as sy,
        (select num from score left join course on score.course_id = course.cid where course.cname = "物理" and score.student_id=sc.student_id) as wl,
        (select num from score left join course on score.course_id = course.cid where course.cname = "体育" and score.student_id=sc.student_id) as ty,
        count(sc.course_id),
        avg(sc.num)
    from score as sc
    group by student_id desc        
 
18、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 course_id, max(num) as max_num, min(num) as min_num from score group by course_id;
 
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 course_id, avg(num) as avgnum,sum(case when score.num > 60 then 1 else 0 END)/count(1)*100 as percent from score group by course_id order by avgnum asc,percent desc;
 
20、课程平均分从高到低显示（现实任课老师）；
 
    select avg(if(isnull(score.num),0,score.num)),teacher.tname from course
    left join score on course.cid = score.course_id
    left join teacher on course.teacher_id = teacher.tid
 
    group by score.course_id
 
 
21、查询各科成绩前三名的记录:(不考虑成绩并列情况)
    select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 3,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
22、查询每门课程被选修的学生数；
     
    select course_id, count(1) from score group by course_id;
 
23、查询出只选修了一门课程的全部学生的学号和姓名；
    select student.sid, student.sname, count(1) from score
 
    left join student on score.student_id  = student.sid
 
     group by course_id having count(1) = 1
 
 
24、查询男生、女生的人数；
    select * from
    (select count(1) as man from student where gender='男') as A ,
    (select count(1) as feman from student where gender='女') as B
 
25、查询姓“张”的学生名单；
    select sname 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 count from student group by sname;
 
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_id,avg(if(isnull(num), 0 ,num)) as avg from score group by course_id order by avg     asc,course_id desc;
 
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 student_id,sname, avg(if(isnull(num), 0 ,num)) from score left join student on score.student_id = student.sid group by student_id;
 
29、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.sname,score.num from score
    left join course on score.course_id = course.cid
    left join student on score.student_id = student.sid
    where score.num < 60 and course.cname = '生物'
 
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 * from score where score.student_id = 3 and score.num > 80
 
31、求选了课程的学生人数
 
    select count(distinct student_id) from score
 
    select count(c) from (
        select count(student_id) as c from score group by student_id) as A
 
32、查询选修“杨艳”老师所授课程的学生中，成绩最高的学生姓名及其成绩；
     
    select sname,num from score
    left join student on score.student_id = student.sid
    where score.course_id in (select course.cid from course left join teacher on course.teacher_id = teacher.tid where tname='张磊老师') order by num desc limit 1;
 
33、查询各个课程及相应的选修人数；
    select course.cname,count(1) from score
    left join course on score.course_id = course.cid
    group by course_id;
 
 
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 DISTINCT s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where s1.num = s2.num and s1.course_id != s2.course_id;
 
35、查询每门课程成绩最好的前两名；
 
    select score.sid,score.course_id,score.num,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num,
        (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 1,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.num <= T.first_num and score.num >= T.second_num
 
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(student_id) > 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,count(1) 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 student_id,student.sname from score
    left join student on score.student_id = student.sid
    where score.course_id not in (
        select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '张磊老师'
    )
    group by student_id
 
39、查询两门以上不及格课程的同学的学号及其平均成绩；
 
    select student_id,count(1) from score where num < 60 group by student_id having count(1) > 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 from score where num< 60 and course_id = 4 order by num desc;
 
41、删除“002”同学的“001”课程的成绩；
    delete from score where course_id = 1 and student_id = 2

 

1、自行创建测试数据

2、查询“数学”课程比“语文”课程成绩高的所有学生的学号；  （内层AS 只能外层使用）

select A.student_id,math,chinese from 
(select student_id,number as math from score LEFT JOIN course on course.cid = score.course_id WHERE course.cname ='数学' ) as A 
INNER JOIN 
(select student_id,number as chinese from score LEFT JOIN course on course.cid = score.course_id WHERE course.cname ='语文') as B
on A.student_id = B.student_id  where math > if(ISNULL(chinese),0,chinese)

3、查询平均成绩大于60分的同学的学号和平均成绩；

select student_id,avg(number) from score GROUP BY student_id HAVING avg(number)>60


4、查询所有同学的学号、姓名、选课数、总成绩；
select score.student_id,student.sname,SUM(score.number),count(score.student_id) from score LEFT JOIN
student on score.student_id=student.sid GROUP BY score.student_id 

5、查询姓“鲁”的老师的个数；

select count(1) from teacher WHERE tname like "鲁%"

select count(tid) from teacher WHERE tname like "鲁%"

6、查询没学过“鲁迅”老师课的同学的学号、姓名；
select * from student where student.sid not in
(select DISTINCT score.student_id from score where score.course_id in
( SELECT cid from course LEFT JOIN teacher on course.teach_id = teacher.tid where teacher.tname = '鲁迅'))

7、查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；
select student.sid,student.sname from student WHERE student.sid in
(SELECT student_id from score where course_id=1 or course_id=2 GROUP BY student_id HAVING COUNT(student_id)=2)

8、查询学过“鲁迅”老师所教的所有课的同学的学号、姓名；
SELECT student.sid,student.sname from student LEFT JOIN score on student.sid = score.student_id WHERE score.course_id in(
 select cid from teacher LEFT JOIN course on teacher.tid = course.teach_id where teacher.tname = '鲁迅')

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；
SELECT A.student_id ,A.sname from 
(select student_id,sname,number from score LEFT JOIN student on score.student_id = student.sid WHERE course_id=1) as A
LEFT JOIN
(select student_id,sname,number from score LEFT JOIN student on score.student_id = student.sid WHERE course_id=2) as B
on A.student_id = B.student_id  WHERE A.number >B.number

10、查询有课程成绩小于60分的同学的学号、姓名；
select student.sid,student.sname from student WHERE student.sid in 
(select DISTINCT student_id from score where score.number<60)

11、查询没有学全所有课的同学的学号、姓名；
SELECT DISTINCT student.sid,student.sname from student 
LEFT JOIN score on student.sid = score.student_id WHERE ISNULL(score.number)


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；
select student.sid,student.sname from student 
LEFT JOIN score on student.sid = score.student_id where score.student_id !=1 and score.course_id in 
(select score.course_id from score where score.student_id = 1) GROUP BY score.student_id3


13查询至少学过学号为“001”同学所选课程中任意一门课的其他同学学号和姓名；
select student.sid,student.sname from student 
LEFT JOIN score on student.sid = score.student_id where score.student_id !=1 and score.course_id in
(select score.course_id from score where score.student_id = 1) GROUP BY score.student_id HAVING COUNT(score.student_id )>=(select COUNT

(score.course_id)from score where score.student_id = 1)

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；
select student.sid,student.sname from student 
LEFT JOIN score on student.sid = score.student_id where score.student_id !=1 and score.course_id in
(select score.course_id from score where score.student_id = 2) GROUP BY score.student_id HAVING COUNT(score.student_id )=(select COUNT

(score.course_id)from score where score.student_id = 2)

15、删除学习“叶平”老师课的SC表记录；
delete from score WHERE score.course_id in 
(select cid from course LEFT JOIN teacher on teacher.tid = course.teach_id where teacher.tname='鲁迅')

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；
insert into score(student_id,course_id,number)
select student.sid,2,(select AVG(score.number) from score WHERE score.course_id=2) from student where student.sid not in 
(select student_id from  score WHERE score.course_id = 2)


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

SELECT sc.student_id,
(SELECT score.number from score LEFT JOIN course on score.course_id = course.cid where course.cname='美术' and score.student_id 

=sc.student_id),
(SELECT score.number from score LEFT JOIN course on score.course_id = course.cid where course.cname='语文' and score.student_id 

=sc.student_id),
(SELECT score.number from score LEFT JOIN course on score.course_id = course.cid where course.cname='数学' and score.student_id 

=sc.student_id),
COUNT(sc.course_id),
AVG(sc.number) as avg

FROM score as sc GROUP BY sc.student_id ORDER BY avg