-- 查询存储引擎
show engines;
-- 显示可用存储引擎
show variables like 'have%';
-- concat多个字段联合
select tname ,cname ,concat(tname,':11',cname ) from  (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where tsex='男';
-- 查出字段间的卡迪尔积
select* from  student ,score
-- std方差
select sno,cno,degree,std(degree)from score where degree in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');
-- group_concat(sname) 查询分组中各项
select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class ;
-- 多个分组查询 先按class分组 再sname相同的再分组
select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class,sname;
-- exists用法
select *from score where  exists (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');
select sno,cno,degree,std(degree)from score where degree  in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');
select *from score where  not exists (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');
-- 获取字符集排列方式
select collation(sname)from student;
-- 获取字符集
select charset(sname)from student;
-- 获取数据库版本号
select version();
-- 获取服务器连接数
select connection_id();
-- 获取数据库的名称
select database();
select schema();
-- 获取用户名
select user();
select system_user();
select session_user();
select current_user;
select current_user();
-- 获取最近生成auto_inscrenment的值
select last_insert_id();
-- 对字符串加密
select password('mrsoft');
-- 普通加密
select md5('mrsoft');
-- 加密
select encode('mrsoft','mr');
-- 解码
select decode('mrsoft','mr');
-- view
create view ccc as select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class,sname;
show create view ccc;
desc ccc;
show table status like 'ccc';

-- 创建数据库mydb3

create DATABASE mydb3 character set utf8;

use  mydb3;

-- 创建数据表Student

create table Student(

		Sno varchar(20) primary key,

		Sname varchar(20) NOT NULL,

		Ssex VARCHAR(20) NOT NULL,

		Sbirthday Datetime,

		Class varchar(20)

);

-- 创建数据表Course

CREATE TABLE Course(

		Cno varchar(20)primary key,

		Cname	varchar(20)NOT NULL,

		Tno varchar(20),

		constraint fk_course_teacher foreign key (tno)references teacher (tno)

);

desc Course;

-- 创建数据表Score

CREATE TABLE Score(

		Sno varchar(20),

		Cno varchar(20),

		Degree Decimal(4,1),

		constraint fk_score_student foreign key (sno)references student (sno),

		constraint fk_score_course foreign key (cno)references course (cno)

);

-- CREATE TABLE Score LIKE Course;

-- 改数据表Score字段

-- ALTER TABLE Score change Tno Degree Decimal(4,1);

desc Score;

-- 创建数据表Teacher

create table Teacher(

		Tno varchar(20)primary key,

		Tname varchar(20)NOT NULL,

		Tsex VARCHAR(20)NOT NULL,

		Tbirthday Datetime,

		Prof varchar(20),

		Depart varchar(20)NOT NULL

);

-- 给数据表Student 添加数据

INSERT INTO Student VALUES(108,'曾华','男','1977-09-01','95033');

INSERT INTO Student VALUES(105,'匡明','男','1975-10-02','95031');

INSERT INTO Student VALUES(107,'王丽','女','1976-01-23','95033');

INSERT INTO Student VALUES(101,'李军','男','1976-02-20','95033');

INSERT INTO Student VALUES(109,'王芳','女','1975-02-10','95031');

INSERT INTO Student VALUES(103,'陆君','男','1974-06-03','95031');

-- 给数据表Course 添加数据

INSERT INTO Course VALUES('3-105','计算机导论','825');

INSERT INTO Course VALUES('3-245','操作系统','804');

INSERT INTO Course VALUES('6-166','数字电路','856');

INSERT INTO Course VALUES('9-888','高等数学','831');

-- 给数据表Score 添加数据

INSERT INTO Score VALUES('103','3-245','86');

INSERT INTO Score VALUES('105','3-245','75');

INSERT INTO Score VALUES('109','3-245','68');

INSERT INTO Score VALUES('103','3-105','92');

INSERT INTO Score VALUES('105','3-105','88');

INSERT INTO Score VALUES('109','3-105','76');

INSERT INTO Score VALUES('101','3-105','64');

INSERT INTO Score VALUES('107','3-105','91');

INSERT INTO Score VALUES('108','3-105','78');

INSERT INTO Score VALUES('101','6-166','85');

INSERT INTO Score VALUES('107','6-166','79');

INSERT INTO Score VALUES('108','6-166','81');

-- 给数据表Teacher 添加数据

INSERT INTO Teacher VALUES(804,'李诚','男','1958-12-02','副教授','计算机系');

INSERT INTO Teacher VALUES(856,'张旭','男','1969-03-12','讲师','电子工程系');

INSERT INTO Teacher VALUES(825,'王萍','女','1972-05-05','助教','计算机系');

INSERT INTO Teacher VALUES(831,'刘冰','女','1977-08-14','助教','电子工程系');

-- 1、 查询Student表中的所有记录的Sname、Ssex和Class列

SELECT Sname,Ssex,Class FROM Student;

-- 2、 查询教师所有的单位即不重复的Depart列

SELECT distinct Depart FROM Teacher;

-- 3、查询Student表的所有记录

select *from Student;

-- 4、 查询Score表中成绩在60到80之间的所有记录。

SELECT *FROM Score WHERE Degree BETWEEN 60 and 80;

-- 5、 查询Score表中成绩为85，86或88的记录。

SELECT * FROM Score WHERE Degree=85 or Degree=86 or Degree=88;

-- 6、 查询Student表中“95031”班或性别为“女”的同学记录。

SELECT *FROM Student WHERE Class=95031 or Ssex='女';

-- 7、以Class降序查询Student表的所有记录。

SELECT * FROM Student ORDER BY Class desc;

-- 8、以Cno升序、Degree降序查询Score表的所有记录。

SELECT * FROM Score ORDER BY Cno asc,Degree desc;

-- 9、查询“95031”班的学生人数。

SELECT COUNT(*) FROM Student WHERE Class=95031;

-- 10、查询每门课的平均成绩。

SELECT  Cname ,AVG(Degree) FROM Score GROUP BY Cname;

-- 11、查询Score表中至少有5名学生选修的并以3开头的课程的平均分数。

select avg(Degree) from Score where Cno like '3%'group by cno HAVING COunt(*)>=5;

select avg(Degree) from Score group by cno HAVING COunt(*)>=5 and  Cno like '3%';

select avg(Degree) from Score where Cno in (select Cno from Score group by Cno having count(*)>5)and Cno like '3%' group by Cno;

select avg(Degree) from Score where Cno in (select Cno from Score where Cno like '3%' ) group by Cno having count(*)>5;

-- 12、查询分数大于70，小于90的Sno列

select sno from score where degree>70 or degree<90;

-- 13查询所有学生的Sname、Cno和Degree列。

select sname,cno,degree from student join score on student.sno=score.sno;

-- 13、查询所有学生的Sno、Cname和Degree列

select sno,cname,degree from course join score on score.cno= course.cno;

-- 15查询所有学生的Sname、Cname和Degree列。

select sname,cname,degree from student join score on student.sno=score.sno join course on score.cno= course.cno ;

-- 16、查询“95033”班学生的平均分。

select avg(degree) from student join score on student.sno=score.sno WHERE class=95033;

select avg(degree) from student join score on student.sno=score.sno group by class having  class=95033;

-- 17、查询和学号为108的同学同年出生的所有学生的Sno、Sname和Sbirthday列。

select sno,sname,sbirthday from student where sno <>108 and YEAR(sbirthday)  in (select YEAR(sbirthday) from student where sno=108);

select Sno,Sname,Sbirthday from Student where YEAR(Sbirthday) = (select YEAR(Sbirthday) from Student where Sno = '108')

-- 18查询“张旭“教师任课的学生成绩（姓名）。

select sname,degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where tname='张旭';

-- 19、查询考计算机导论的学生成绩

select sname,degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where cname='计算机导论';

-- 20、查询李诚老师教的课程名称

select distinct cname from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where tname='李诚';

-- 21、教高等数学的老师是哪个系的

select depart from teacher join course on teacher.tno= course.tno where cname='高等数学';

-- 22、查询选修某课程的同学人数多于5人的教师姓名。

select tname from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) group by cname having count(*)>5;

-- 23、查询95033班和95031班全体学生的记录

select * from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where class=95033 or class=95031;

-- 24查询存在有85分以上成绩的课程Cno.

select distinct cno  from score where degree>85;

-- 25、查询出“计算机系“教师所教课程的成绩表

select sno,cno,degree from score where degree in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

-- 26、 查询所有教师和同学的name、sex和birthday.

select tname as name, tsex as sex,tbirthday as birthday from teacher

union  select sname,ssex, sbirthday from student;

-- 27、查询所有“女”教师和“女”同学的name、sex和birthday.

select tname as name, tsex as sex,tbirthday as birthday from teacher where tsex='女'

union  select sname,ssex, sbirthday from student where ssex='女';

-- 28查询所有任课教师的Tname和Depart.

select tname,depart from teacher where tno in (select tno from course);

-- 29、查询所有未讲课的教师的Tname和Depart.

select tname,depart from teacher left join(student join score on student.sno=score.sno join course on score.cno= course.cno ) on teacher.tno= course.tno where degree is null;

select tname,depart from teacher where tno not in (select tno from course where cno in (select cno from score))

-- 30、查询至少有2名男生的班号。

select class from student where ssex='男' GROUP BY class having count(*)>=2;

-- 31、查询Student表中不姓“王”的同学记录。

select * from student where sname not in (select sname from student where sname like '王%');

-- 32、查询Student表中每个学生的姓名和年龄

select sname,(year(now())-year(Sbirthday))as 年龄 from student;

-- 33、查询Student表中最大和最小的Sbirthday日期值

select max(Sbirthday),min(Sbirthday) from student;

-- 34、以班号和年龄从大到小的顺序查询Student表中的全部记录

select *from student order by class desc,Sbirthday asc;

-- 35、查询“男”教师及其所上的课程。

select DISTINCT tname ,cname from  (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where tsex='男';

-- 36、查询最高分同学的Sno、Cno和Degree列。

select sno,cno,max(degree) from score;

-- 37、查询和“李军”同性别的所有同学的Sname.

select sname from student where ssex=(select ssex from student where sname='李军');

-- 38、查询和“李军”同性别并同班的同学Sname.

select sname from student where ssex=(select ssex from student where sname='李军')

and class=(select class from student where sname='李军');

-- 39、查询所有选修“计算机导论”课程的“男”同学的成绩表。

select sno,cno,degree from score where degree in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where cname='计算机导论'and ssex='男');

select   year(CURRENT_DATE () )

select getdate()

-- 查询存储引擎

show engines;

-- 显示可用存储引擎

show variables like 'have%';

-- concat多个字段联合

select tname ,cname ,concat(tname,':11',cname ) from  (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where tsex='男';

-- 查出字段间的卡迪尔积

select* from  student ,score

-- std方差

select sno,cno,degree,std(degree)from score where degree in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

-- group_concat(sname) 查询分组中各项

select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class ;

-- 多个分组查询 先按class分组 再sname相同的再分组

select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class,sname;

-- exists用法

select *from score where  exists (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

select sno,cno,degree,std(degree)from score where degree  in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

select *from score where  not exists (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

-- 获取字符集排列方式

select collation(sname)from student;

-- 获取字符集

select charset(sname)from student;

-- 获取数据库版本号

select version();

-- 获取服务器连接数

select connection_id();

-- 获取数据库的名称

select database();

select schema();

-- 获取用户名

select user();

select system_user();

select session_user();

select current_user;

select current_user();

-- 获取最近生成auto_inscrenment的值

select last_insert_id();

-- 对字符串加密

select password('mrsoft');

-- 普通加密

select md5('mrsoft');

-- 加密

select encode('mrsoft','mr');

-- 解码

select decode('mrsoft','mr');

-- view

create view ccc as select class,AVG(degree),group_concat(sname)from student join score on student.sno=score.sno group by class,sname;

show create view ccc;

desc ccc;

show table status like 'ccc';

explain select sno,cno,degree,std(degree)from score where degree  in (select degree from (student join score on student.sno=score.sno join course on score.cno= course.cno join teacher on teacher.tno= course.tno) where depart='计算机系');

　　

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