–1.查询与“张志国”同一班级的学生信息(使用连接查询和子查询方式)

	--连接查询(子连接查询)
select X.SNo,X.SN,X.Sex,X.Class,X.Birthday,X.Phone
from S as X,S as Y
where Y.SN='张志国' and X.Class=Y.Class and X.SN!='张志国'
	
	--子查询
select * from S where Class = (
	select Class from S where SN='张志国') and SN!='张志国'

–2.查询比“计算机应用基础”学时多的课程信息(使用连接查询和子查询方式)

	--连接查询
select X.CNo,X.CN,X.Credit,X.CT,X.Teach
from C as X,C as Y
where Y.CN='计算机应用基础' and X.CT>Y.CT
	
	--子查询
select * from C where CT>(
	select CT from C where CN='计算机应用基础')

–3.查询选修课程号为K002的学生的学号、姓名(使用连接查询、普通子查询、相关子查询、使用exists关键字的相关子查询)

	--连接查询(内连接查询)
select R1.SNo,R1.SN
from
(select SNo,SN from S) as R1
inner join
(select CNo,SNo from SC
where CNo='K002') as R2
on R1.SNo=R2.SNo
	
	--普通子查询
select SNo,SN from S where SNo in(
	select SNo from SC where CNo='K002')
	
select SNo,SN from S where SNo=any(
	select SNo from SC where CNo='K002')
	
	--相关子查询
select SNo,SN from S where SNo in(
	select SNo from SC where CNo='K002' and SNo=S.SNo)
	
	--使用exists关键字的相关子查询
select SNo,SN from S where exists(
	select * from SC where CNo='K002' and SNo=S.SNo)

–4.查询没有选修K001和M001课程的学号、课程号和三次成绩(使用子查询)

	--子查询(普通子查询)
select SNo,CNo,Score_1,Score_2,Score_3
from SC 
where CNo not in ('K001','M001')

–5.在学生表中添加一条学生记录，其中，学号为1593，姓名为张乐，性别为男，专业班级为电子05

insert into S(SNo,SN,Sex,Class)
	values(1593,'张乐','男','电子05')

–6.将所有课程的学分数变为原来的两倍

update C
set Credit=Credit*2

–7.删除张乐的信息

delete 
from S 
where SN='张乐'