SQL Server 数据查询

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前言

首先在SQL Server 2008 中新建一个数据库chaxun.在库中建三个表,结构如下表所示,并且录入数据.

1.

CREATE DATABASE  chaxun
ON PRIMARY                     
(NAME=chaxun_data,              
 FILENAME='D:\software\chaxun.mdf',
 SIZE=10MB,
 MAXSIZE=UNLIMITED,           
 FILEGROWTH=10% 
)
 LOG ON 
 (NAME=chaxun_log,
  FILENAME='D:\software\chaxun.ldf',

  SIZE=1MB,
  MAXSIZE=5MB,
  FILEGROWTH=1MB
 )

 use chaxun 
  create table KC
(
c_ID char(3) primary key,
c_Name char(10) not null,
c_Credit int
)

create table XS
(
s_ID char(4) primary key,
s_Name char(6) not null,
s_department char(20) not null,
s_telephoe char(11)
)


create table XS_KC
(
s_ID char(4) foreign key references XS(s_ID),
c_ID char(3) foreign key references KC(c_ID),
score int,
primary key(s_ID,c_ID)
)

KC表数据：

insert into KC values('101','语文',4)
insert into KC values('102','数学',2)
insert into KC values('103','英语',3)
insert into KC values('104','体育',1)

XS表数据：

insert into XS values('1001','杨颖','信息技术系','2346666')
insert into XS values('1002','王丽','信息技术系','2346666')
insert into XS values('1003','张亮','经管系','2315555')
insert into XS values('1004','刘强','会计系','2361111')

XS_KC表数据：

insert into XS_KC values('1001','101',89)
insert into XS_KC values('1001','102',97)
insert into XS_KC values('1001','103', 86)
insert into XS_KC values('1002', '101',56)
insert into XS_KC values('1003', '102',55)

2.

(1)在KC表中查询学分低于三分的课程信息，并按课程号升序排列

select * from KC
where C_Credit<3 order by c_ID ASC

(2)在XS_KC表中按学号分组汇总学生的平均分，并按平均分的降序排列

select s_ID,AVG(score) 平均分 from XS_KC 
group by s_ID
order by AVG(score) DESC

(3)在XS_KC表中查询至少选修了2门课程的学生学号和姓名

select  s_Name,XS.s_ID from XS_KC,XS  where XS.s_ID=XS_KC.s_ID
group by XS.s_ID,s_Name having COUNT(XS_KC.c_ID)>=2

(4)查询成绩不及格的学生的基本信息

方法1

select XS.* from XS,XS_KC
where XS.s_ID=XS_KC.s_ID and score<60

方法2(子查询)

select * from XS where s_ID in (select s_ID from XS_KC where score<60)

(5)分别用子查询和连接查询，查询101号课程不及格的基本信息

子查询

select * from XS where s_ID in(select distinct s_ID from XS_KC
where XS_KC.c_ID='101' and score <60)

连接查询

select XS.* from XS join XS_KC on XS.s_ID=XS_KC.s_ID  
where XS_KC.c_ID='101' and score <60

(6)在XS表中查询住在同一宿舍的学生信息，即其所住宿舍电话相同

select * from XS where s_telephoe in 
(select  s_telephoe from XS group by s_telephoe having COUNT(s_telephoe)>=2)

(7)查询XS表中的所有系名

select distinct s_department from XS

(8)查询有多少名同学选修了课程

select COUNT(distinct s_ID ) 已选课人数 from XS_KC

(9)查询与杨颖同在一个系的同学姓名

方法1

select x.s_Name from XS as x,XS as y
where x.s_department=y.s_department and y.s_Name='杨颖' and x.s_Name<>'杨颖'

方法2

select s_Name from XS where s_department=
(select s_department from XS where s_Name='杨颖') and s_Name <>'杨颖'

(10)查询选修了课程的学生的姓名、课程名与成绩

方法1

select s_Name,c_Name,score from XS,KC,XS_KC
where XS.s_ID=XS_KC.s_ID and KC.c_ID=XS_KC.c_ID

方法2

select s_Name,c_Name,score from XS join XS_KC on XS.s_ID=XS_KC.s_ID
join KC on KC.c_ID=XS_KC.c_ID

(11)修改经管系电话号码为3615555

update XS set s_telephoe='3615555' where s_department='经管系'

(12)统计每门课程的选课人数和最高分

select c_ID,COUNT(s_ID) 选课人数,MAX(score) 最高分 from XS_KC group by c_ID

(13)统计每个学生的选课门数和考试总成绩，并按选课门数的降序排列

select s_ID,COUNT(c_ID) 选课门数,SUM(score) 总成绩 from XS_KC
group by s_ID order by COUNT(c_ID) DESC

(14)查询有多少名学生没有选课

select COUNT(s_ID) 未选课人数 from XS where s_ID not in 
(select s_ID from XS_KC)

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总结

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