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+某某学校为了让学生学习mysql，安排你建立一个用于统计成绩和课程的数据库，数据库要求如下：
+
+数据库库名： mtyk
+
+创建四个表：
+
+教师表 (J_TEACHER)
+
+Tno 主键 自增 备注为教师编号
+
+Tname 不可重复 备注为教师姓名
+
+学生表(J_STUDENT)
+
+Sno 主键 自增 备注为学生编号
+
+Sname 不可重复 备注为学生姓名
+
+Sage 备注为学生年龄
+
+Ssex 男or女 备注为性别
+
+课程表(J_COURSE)
+
+Cno 主键 自增 备注为课程编号
+
+Cname 不可重复 备注为课程名称
+
+Tno 外键 备注为授课教师编号 关联J_TEACHER表主键
+
+成绩表(J_SCORE)
+
+Sno 外键 备注为学生编号 关联J_STUDENT表主键
+
+Cno 外键 备注为课程编号 关联J_COURSE 表主键
+
+Score 备注为成绩
+
+![img]()
+
+```mysql
+create database mtyk charset utf8;
+
+use mtyk;
+
+create table J_TEACHER(
+	Tno int primary key auto_increment comment '教师编号',
+	Tname varchar(20) unique comment '教师姓名'
+);
+
+insert into J_TEACHER values
+(1,'张老师'),
+(2,'王老师'),
+(3,'李老师'),
+(4,'赵老师'),
+(5,'刘老师'),
+(6,'向老师'),
+(7,'李文静'),
+(8,'叶平');
+
+create table J_STUDENT(
+	Sno int primary key auto_increment comment '学生编号',
+	Sname varchar(20) unique comment '学生姓名',
+	Sage datetime comment '学生年龄',
+	Ssex enum('男','女') comment '性别'
+);
+
+insert into J_STUDENT values
+(1,'张三','1980-1-23 00:00:00','男'),
+(2,'李四','1982-12-12 00:00:00','男'),
+(3,'张飒','1981-9-9 00:00:00','男'),
+(4,'莉莉','1983-3-23 00:00:00','女'),
+(5,'王粥','1982-6-21 00:00:00','男'),
+(6,'王丽','1984-10-10 00:00:00','女'),
+(7,'刘香','1980-12-22 00:00:00','女');
+
+create table J_COURSE(
+	Cno int primary key auto_increment comment '课程编号',
+	Cname varchar(20) unique comment '课程名称',
+	Tno int comment '授课教师编号',
+	foreign key (Tno) references J_TEACHER(Tno)
+);
+
+insert into J_COURSE values
+(1,'企业管理',3),
+(2,'马克思',1),
+(3,'美团盈开',2),
+(4,'数据库',5),
+(5,'物理',8);
+
+create table J_SCORE(
+	Sno int comment '学生编号',
+	Cno int  comment '课程编号',
+	Score int comment '成绩',
+	foreign key (Sno) references J_STUDENT(Sno),
+	foreign key (Cno) references  J_COURSE (Cno)
+);
+
+insert into J_SCORE values 
+(1,1,80),
+(1,2,86),
+(1,3,83),
+(1,4,89),
+(2,1,50),
+(2,2,36),
+(2,3,43),
+(2,4,59),
+(3,1,50),
+(3,2,96),
+(3,3,73),
+(3,4,69),
+(4,1,90),
+(4,2,36),
+(4,3,88),
+(4,4,99),
+(5,1,90),
+(5,2,96),
+(5,3,98),
+(5,4,99),
+(6,1,70),
+(6,2,66),
+(6,3,58),
+(6,4,79),
+(7,1,80),
+(7,2,76),
+(7,3,68),
+(7,4,59),
+(7,5,89);
+```
+
+1、 修改刘香的美团盈开课程成绩为100分
+
+```mysql
+update J_SCORE set score=100 where sno=(select sno from J_STUDENT where sname='刘香') and cno=(select cno from J_COURSE where cname='美团盈开');
+```
+
+2、 将学生表中的sage段放在ssex段后面
+
+```mysql
+alter table J_STUDENT modify Sage datetime after Ssex;
+```
+
+3、 教师表添加一个用于统计状态的列 名字为now 默认值为有课
+
+```mysql
+alter table J_TEACHER add now varchar(20) default '有课';
+```
+
+4、 将没有上课的老师的now列值设置为无课
+
+```mysql
+update J_TEACHER set now='无课' where tno not in (select tno from J_COURSE);
+```
+
+5、 修改课程表中的企业管理为比遛旺
+
+```mysql
+update J_COURSE set cname='比遛旺' where cname='企业管理';
+```
+
+6、 查询课程1的成绩比课程2的成绩 高 的所有学生的学号。
+
+```mysql
+select s.sno from J_SCORE s join J_SCORE c on s.sno=c.sno where s.cno=1 and c.cno=2 and s.score>c.score;
+
+select a1.sno from (select * from J_SCORE where cno=1) a1 left join (select * from J_SCORE where cno=2) a2 on a1.sno=a2.sno where a1.score>a2.score;
+```
+
+7、 查询平均成绩大于60分的同学的学号和平均成绩。
+
+```mysql
+select sno,avg(score) from J_SCORE group by sno having avg(score)>60;
+```
+
+8、 查询所有同学的学号、姓名、选课数、总成绩。
+
+```mysql
+select jst.sno,sname,count(cno),sum(score)  from J_STUDENT jst left join J_SCORE jsc on jst.sno=jsc.sno group by jsc.sno;
+```
+
+9、 查询姓“李”的学生的个数。
+
+```mysql
+select count(sname) from J_STUDENT where sname like '李%';
+```
+
+10、 查询没学过“叶平”老师课的同学的学号、姓名。
+
+```mysql
+select j_score.sno,sname from j_student left join j_score on j_student.sno=j_score.sno where j_score.sno in (select sno from  j_score where sno!=(select sno from j_score  where cno = (select cno from j_course where tno=(select tno from j_teacher where tname='叶平'))) GROUP BY sno) GROUP BY sno;
+```
+
+11、 查询同时学过课程1和课程2的同学的学号、姓名。
+
+```mysql
+select jst.sno,jst.sname from J_STUDENT jst left join  (select * from J_SCORE where cno=1) a1 on jst.sno=a1.sno left join (select * from J_SCORE where cno=2) a2 on a1.sno=a2.sno;
+
+SELECT a.sno,a.sname from j_student a where a.sno in ( select b.sno from j_score b JOIN j_score c on b.sno=c.sno where b.cno=1 and c.cno=2);
+```
+
+12、 查询学过“叶平”老师所教所有课程的所有同学的学号、姓名。
+
+```mysql
+select j_score.sno,sname from j_student left join j_score on j_student.sno=j_score.sno where j_score.sno in (select sno from  j_score where sno=(select sno from j_score  where cno = (select cno from j_course where tno=(select tno from j_teacher where tname='叶平'))) GROUP BY sno) GROUP BY sno;
+```
+
+13、 查询 课程编号1的成绩 比 课程编号2的成绩 高的所有同学的学号、姓名。
+
+```mysql
+select jst.sno,jst.sname from J_STUDENT jst right join J_SCORE a on jst.sno=a.sno join J_SCORE b on a.sno=b.sno where a.cno=1 and b.cno=2 and a.score>b.score;
+```
+
+14、 查询所有课程成绩小于60分的同学的学号、姓名。
+
+```mysql
+select a.sno,a.sname from j_student as a where a.sno in ( select b.sno from j_score as b group by b.sno having max(b.score)<60);
+```
+
+15、 查询所有课程成绩大于60分的同学的学号、姓名。
+
+```mysql
+select a.sno,a.sname from j_student as a where a.sno in ( select b.sno from j_score as b group by b.sno having max(b.score)>60);
+```
+
+16、 查询没有学全所有课的同学的学号、姓名
+
+```mysql
+select J_SCORE.sno,sname from J_SCORE left join J_STUDENT on J_STUDENT.sno = J_SCORE.sno group by J_SCORE.sno having not count(J_SCORE.sno)=(select count(cno) from J_COURSE);
+```
+
+17、 查询至少有一门课程 与 学号为1的同学所学课程 相同的同学的学号和姓名
+
+```mysql
+select sno,sname from J_STUDENT where sno in (select sno from J_SCORE where cno in (select cno from J_SCORE where sno=1) and sno!=1);
+```
+
+18、 查询和2号同学学习的课程完全相同的其他同学学号和姓名。
+
+```mysql
+select sno,sname from J_STUDENT where sno in (select sno from J_SCORE where cno in (select cno from J_SCORE where sno=2) and sno!=2);
+```
+
+19、 查询各科成绩最高分和最低分。
+
+```mysql
+select cno,max(score),min(score) from J_SCORE group by cno;
+```
+
+20、 查询每门课程被选修的学生数。
+
+```mysql
+select cno,count(sno) from J_SCORE group by cno;
+```
+
+21、 查询出只选修了一门课程的全部学生的学号和姓名。
+
+```mysql
+select sno,sname from J_STUDENT where sno in (select sno from J_SCORE group by sno having count(cno)=1);
+```
+
+22、 查询同名同性学生名单，并统计同名人数。
+
+```mysql
+select sname,ssex,count(sname) from (select a.sname,a.ssex from J_STUDENT a join J_STUDENT b on a.sname=b.sname where a.sname=b.sname and a.sno!=b.sno and a.ssex=b.ssex) c group by sname,ssex;
+```
+
+23、 查询选修“叶平”老师所授课程的学生中，成绩最高的学生姓名及其成绩。
+
+```mysql
+select max(score),sname from J_STUDENT jst left join J_SCORE jsc on jst.sno=jsc.sno right join J_COURSE jco on jsc.cno=jco.cno left join J_TEACHER jte on jco.tno=jte.tno where tname='叶平';
+```
+
+24、 查询不同课程成绩相同的学生的学号、课程号、学生成绩。
+
+```mysql
+select a.sno,a.cno,a.score from J_SCORE a join J_SCORE b on a.sno=b.sno where a.cno!=b.cno and a.score=b.score;
+```
+
+25、 查询每门课程成绩最好的前两名的学生ID
+
+```mysql
+select a.sno,a.cno,a.score from j_score a where (select count(*) from j_score b where a.cno=b.cno and a.score<=b.score)<=2;
+```
+
+26、 检索至少选修了5门课程的学生学号。
+
+```mysql
+select sno from J_SCORE group by sno having count(sno)>=5;
+```
+
+27、 查询没学过“叶平”老师讲授的任一门课程的学生姓名。
+
+```mysql
+select jst.sno,jst.sname from J_STUDENT jst left join J_SCORE jsc on jst.sno=jsc.sno left join J_COURSE jco on jsc.cno=jco.cno left join J_TEACHER jte on jco.tno=jte.tno where tname !='叶平' group by jst.sname;
+```
+
+28、 查询两门以上不及格课程的同学的学号及其平均成绩。
+
+```mysql
+select sno,avg(score) from J_SCORE where score<60 group by sno having count(sno)>2;
+```
+
+29、 查询最受欢迎的老师(选修学生最多的老师)。
+
+```mysql
+select tname from J_SCORE a,J_COURSE,J_TEACHER where a.cno=J_COURSE.cno and J_TEACHER.tno=J_COURSE.tno group by a.cno having count(a.cno)=(select max(c.b) from (select count(cno) b from J_SCORE group by cno) c);
+```
+
+30、 修改课程表名为给乱给要酒要
+
+```mysql
+alter table J_COURSE rename to 乱给要酒要;
+```
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