mysql數據庫查詢練習

創建四張數據表

學生表student：學號，姓名，性別，出生年月日，所在班級

教師表teacher：教師編號，教師名，教師性別，出生年月日，職稱，所在部門

課程表course：課程號，課程名，教師編號

成績表score：學號，課程號，成績

添加信息：

學生表：

insert into student values ('1001','老大','男','1999-08-01','2000');
insert into student values ('1002','老二','女','1999-08-02','2000');
insert into student values ('1003','老三','男','1999-08-03','2001');
insert into student values ('1004','老四','女','1999-08-04','2001');
insert into student values ('1005','老五','男','1999-08-05','2002');
insert into student values ('1006','老六','男','1999-08-06','2002');
insert into student values ('1007','老七','男','1999-08-07','2003');
insert into student values ('1008','老八','女','1999-08-08','2004');

教師表：

insert into teacher values('201','王菊','女','1890-10-11','副教授','計算機系');
insert into teacher values('202','李平','男','1890-10-11','教授','電子工程系');
insert into teacher values('203','張利','男','1890-10-11','副教授','自動化系');
insert into teacher values('204','王霞','女','1890-10-11','講師','電子工程系');
insert into teacher values('205','劉傑','男','1890-10-11','助教','計算機系');

課程表：

insert into course values ('3-101','計算機基礎','201');
insert into course values ('3-102','高等數學','202');
insert into course values ('3-103','操作系統','203');
insert into course values ('3-104','概率論','204');
insert into course values ('3-105','概率論','205');

成績表：

insert into score values ('1001','3-101','98');
insert into score values ('1001','3-103','97');
insert into score values ('1002','3-101','88');
insert into score values ('1003','3-104','78');
insert into score values ('1004','3-103','98');
insert into score values ('1006','3-101','77');
insert into score values ('1008','3-104','55');
insert into score values ('1001','3-102','98');
insert into score values ('1007','3-105','67')

查詢練習：

1.查詢student表的所有記錄；

select * from student

　

2.查詢student表的sname，ssex,class列；

select sname,ssex,class from student 

　

3.查詢教師所有的部門，不重復顯示

select distinct depart  from teacher 

　

4.查詢成績表中成績在77-88之間的所有記錄

select *  from score  where degree between '77' and '88'

由查詢的數據可知，between...and查詢的結果包括兩端的值 

select *  from score  where degree>77 and degree<88

　

 由查詢數據可知，直接使用運算符比較不包含兩端數據 

5.查詢成績為98，88，或77的記錄

select *  from score  where degree = '77' or degree = '88' or degree = '98'

select *  from score  where degree  in (77,88,98)　　（in表示或者的關系）

6.查詢學生表中1001班或性別為女的學生記錄

select *  from student  where class='2000' or ssex = '女'

 

7.以class降序查詢學生表的所有記錄

select *  from student  order by class desc

 

8.以cno升序，degree降序查詢成績表的所有記錄

select *  from score  order by cno asc , degree desc 

9.查詢2000班的所有學生人數

select count(*) from student where class = 2000

10.查詢成績表中的最高分的學生號和課程號（子查詢）

select sno,cno from score where degree=(select max(degree) from score)

 11.查詢每門課的平均成績（分組查詢group by）

select cno,avg(degree)from score group by cno 

12.查詢score 表中至少有2名學生選修的並以3開頭的課程的平均成績（具有條件的分組查詢group by....having，模糊查詢）

select cno,count(cno),avg(degree) from score group by cno having count(cno)>=2 and cno like'3%'

13.查詢分數大於70，小於90的sno列

select sno,degree from score where degree between 70 and 90

select sno,degree from score where degree>70 and degree<90

 14.查詢所有學生的sname,cno,degree列（多表查詢）

select sname,cno,degree from student,score where student.sno = score.sno

 

 15.查詢所有學生的sno,cname,degree的列（多表聯查）

select sno,cname,degree from course,score where course.cno = score.cno

 

 16.查詢所有學生的sname,cname,degree(三表聯查，找到一個中間表，另兩個表與中間表產生聯系)

select sname,cname,degree from student,course,score where student.sno= score.sno and course.cno = score.cno

 17.查詢“2000”班學生每門課的平均成績

（1）2000班的學生的學號

select * from student where class='2000'

select  sno  from student where class='2000'

(2)根據（1）學生號查詢2000班的學生成績表

select * from score where sno in (select sno from student where class='2000')

select cno,degree from score where sno in (select sno from student where class='2000')

（3）根據（2）中的cno對學科進行分組求平均分

select cno,avg(degree) from score where sno in (select sno from student where class='2000') group by cno

 

 18.查詢選修“3-101”課程的成績高於“1006”號同學選修“3-101”成績的所有同學的記錄

（1）查選“1006”號同學選修3-101課的成績

select * from score where cno='3-101' and sno='1006'

（2）查詢選修“3-101”課程的成績高於“1006”號同學選修“3-101”成績的所有同學的記錄

select * from score where degree>(select degree from score where cno='3-101' and sno='1006')and cno='3-101'

 19.查詢成績高於學號“1006”、課程號為“3-101”的成績的所有記錄

（1）查選“1006”號同學選修3-101課的成績

select * from score where cno='3-101' and sno='1006'

（2）查詢成績高於學號“1006”、課程號為“3-101”的成績的所有記錄

select * from score where degree>(select degree from score where cno='3-101' and sno='1006')

 

 20.查詢學號為1008、1001的同學的同年出生的所有學生的sno\sname\sbrithday列

（1）查詢學號為1008、1001的同學的同年出生
select year(sbrithday) from student where sno in ('1001','1008')

（2）查詢學號為1008、1001的同學的同年出生的所有學生的sno\sname\sbrithday列
select sno,sname,sbrithday from student where year(sbrithday) =(select year(sbrithday) from student where sno in ('1001','1008'))

 21.查詢王菊老師任課的學生成績

（1）查詢王菊老師的課程號

select cno from teacher as t,course as c where t.tno=c.tno

（2）查詢王菊老師任課的學生成績

select sno,degree from score where cno=(select cno from teacher as t,course as c where t.tno=c.tno and tname='王菊')

 22.查詢選修某課程的學生人數多於2人的教師姓名

（1）根據課程號查詢選修人數大於2人的課程號（group by的條件分組查詢）

select cno from score  group by cno having count(cno)>2

（2）根據（1）查詢出課程表中的教師號

select tno from course where cno =(select cno from score group by cno having count(cno)>2)

（3）根據教師號查詢教師名字

select tname from teacher where tno=(select tno from course where cno =(select cno from score group by cno having count(cno)>2))

 23.查詢2000班和2001班的學生記錄（或的使用，In，or）

select * from student where class in('2000','2001')

select * from student where class ='2000' or class='2001'

　24.查詢計算機系老師所教課程的成績

（1）查詢計算機系老師的教師號

select tno from teacher where depart='計算機系'

（2）根據教師號查詢老師對應的課程號

select cno from course where tno in (select tno from teacher where depart='計算機系')

（3）根據課程號查詢成績

select cno,degree from score where cno in (select cno from course where tno in (select tno from teacher where depart='計算機系'))

 25.查詢計算機系和電子工程系不同職稱的教師姓名和職稱prof（這兩個系中職稱相同的舍去）

（1）查詢電子工程系的所有老師的職稱

select prof from teacher where depart = '計算機系'

　　  查詢計算機系的所有老師的職稱

select prof from teacher where depart = '電子工程系'

（2）查詢計算機系中與電子工程系中不同的職稱

select prof from teacher where depart = '計算機系' and prof not in (select prof from teacher where depart = '電子工程系')

　　  查詢電子工程系中與計算機系中不同的職稱

select prof from teacher where depart = '電子工程系' and prof not in (select prof from teacher where depart = '計算機系')

（3）使用union將（2）中的語句進行聯合（求並集），得出兩個系中不同的職稱

select prof from teacher where depart = '電子工程系' and prof not in (select prof from teacher where depart = '計算機系')

union

select prof from teacher where depart = '計算機系' and prof not in (select prof from teacher where depart = '電子工程系')

 

 26.查詢選修編號為“3-101”課程且成績至少高於選修編號為“3-102”的同學的cno,sno,degree,並按成績由高到底排列

（1）查詢出選修“3-102”學生的成績

select degree from score where cno='3-102'

（2）查詢出選修3-101課程的成績至少大於3-102的學生cno,sno,degree的信息（至少any：只需要滿足3-101中的成績大於3-102中的最低成績即可）

select cno,sno,degree from score where degree>any(select degree from score where cno='3-102') and cno ='3-101'

（3）根據（2）的成績降序排列（order by  ... desc）

select cno,sno,degree from score where degree>any(select degree from score where cno='3-102') and cno ='3-101' order by degree desc

 27.查詢選修編號為“3-101”課程且成績高於選修編號為“3-102”的同學的cno,sno,degree

（1）查詢出選修“3-102”學生的成績

select degree from score where cno='3-102'

（2）查詢出選修3-101課程的成績大於3-102的學生cno,sno,degree的信息（且all:高於3-102班的最高成績才滿足）

select cno,sno,degree from score where degree>all(select degree from score where cno='3-102') and cno ='3-101'

 28.查詢所有教師和學生的name,sex,brithday(求並集union)

select sname as name,ssex as sex,sbrithday as brithday from student 
union 
select tname as name,tsex as sex,tbrithday as brithday from teacher

29.查詢成績比該成績平均分低的同學的成績表

（1）查詢每一門課的平均成績

select  avg(degree) from score b group by cno

（2）通過采用復制表結構的方法做條件查詢（保證使用的cno是相同的）

select * from score a where degree<(select avg(degree) from score b where a.cno=b.cno)

30.查詢至少有兩名男生的班級

select  count(ssex),class from student where ssex='男' group by class having count(ssex)>=2

 31.查詢student表中不含“老”字的同學記錄

select * from student where sname not like'老%'

32.查詢student表中每個學生的姓名和年齡

年齡=當前年份-出生年份

（1）當前年份

select year(now())

（2）學生出生年份

select year(sbrithday) from student 

（3）每個學生的姓名和年齡

select sname,year(now())-year(sbrithday) as age from student

 

 33.以班號和年齡從大到小查詢student表中所有同學的信息

select * from student  order by class desc,sbrithday

34.按等級查詢

創建一個等級表

create  table grade(low int(3),upp int(3),grade char(4))

插入數據

insert into grade values (90,100,'a');

insert into grade values (80,89,'b');

insert into grade values (70,79,'c');

insert into grade values (60,69,'d');

insert into grade values (0,59,'e');

查詢所有學生的sno,cno,grade

select sno,cno,grade from score,grade where score.degree between grade.low and grade.upp

 35.sql的四種連接查詢

內連接：inner join 或 join

外連接：

左外連接：left join ...on或 left outer join ...on

右外連接：right join...on 或 right outer join...on

完全外連接：full join...on 或 full outer join...on

創建兩張表：

person 表：id,name,cardId

card 表 ：id，name

create table person (id int (10) primary key ,name varchar(20),cardid int(10) );

create table card (id int(10) primary key ,name varchar (20) );

向兩張表中分別添加數據

insert into card values(1,'飯卡');

insert into card values(2,'地鐵卡');

insert into card values(3,'工商卡');

 insert into card values(4,'郵政卡');

insert into card values(5,'農行卡');

insert into person values(1,'老大',1);

insert into person values(2,'老二',4);

insert into person values(3,'老三',5);

insert into person values(4,'老四',2);

insert into person values(5,'老五',2);

insert into person values(6,'老六',6);

注意到person表中並沒有創建外鍵

（1）內連接（jion ...on）,查詢出兩張表有關聯的信息（即兩表共有的部分）

 select * from person join card on person.cardId=card.id

 select * from person inner join card on person.cardId=card.id

（2）左外連接：會把左邊表里的所有數據取出來，而右邊表中的數據，如果有相等的就顯示出來，若沒有就顯示為空

select * from person left join card on person.cardId=card.id

（3）右外連接：會把右邊表里的所有數據取出來，而左邊表中的數據，如果有相等的就顯示出來，若沒有就顯示為空

select * from person right join card on person.cardId=card.id

 

（4）全外連接（full join ）,注:Mysql 默認不支持此種寫法 Oracle支持(select * from person full join card on person.cardId=card.id) ,可以使用將左連接與右連接結合起來作為全連接

select * from person right join card on person.cardId=card.id
union 

select * from person left join card on person.cardId=card.id