Mysql基础知识点汇总

2019-01-04 20:53:14王旭

 select * from Student where Sex=@sex and ClassId=@classid
set @cnt= (select COUNT(*) from Student where Sex=@sex and ClassId=@classid) --获取指定班级和性别的总人数
set @totalnum=(select COUNT(*) from Student) ----获取总人数
go
--调用存储过程,获取指定性别的学员人数及总人数
declare @num int,@tnum int
exec usp_getCountBySexandClassName @cnt=@num output ,@totalnum=@tnum output , @className='八期班'
print @num
print @tnum
print '做完了'
---获取指定班级的人数
if exists(select * from sysobjects where name='usp_getCount')
 drop proc usp_getCount
go
create procedure usp_getCount
 @className nvarchar(50)='八期班'
as
declare @classid int=(select classid from grade where classname=@className)
 declare @cnt int
set @cnt =(select COUNT(*) from Student where ClassId=@classid)
--return 只能返回int整数值
--return '总人数是'+cast(@cnt as varchar(2))
return @cnt
go

--调用存储过程,接收存储过程的返回值
declare @count int
--set @count=(exec usp_getCount)
exec @count=usp_getCount '八期班'
print @countif exists(select*from sysobjects where name='usp_getClassList')
 drop proc usp_getClassList
go
create procedure usp_getClassList
asselect classid,classname from grade
go

21.分页存储过程

if exists(select * from sysobjects where name='usp_getPageData')
 drop proc usp_getPageData
go
create procedure usp_getPageData
@totalPage int output,--总页数
@pageIndex int =1 ,--当前页码,默认是第一页
@pageCount int =5 --每一页显示的记录数
as
select * from (select ROW_NUMBER() over(order by studentno) id,* from Student) temp where temp.id>(@pageindex-1)*@pagecount and temp.id<=(@pageindex*@pagecount)
set @totalPage=CEILING((select COUNT(*) from Student)*1.0/@pageCount)
go

22.索引

select * from sysindexes

--create  index IX_Student_studentName
--on 表名(字段名)

--clustered index:聚集索引  nonclustered index--非聚集索引
if exists(select * from sysindexes where name='IX_Student_studentName')
 drop index student.IX_Student_studentName
go
create clustered index IX_Student_studentName
on student(studentname)

--如果是先创建主键再创建聚集索引就不可以,因为主键默认就是聚集索引
--但是如果先创建聚集索引,那么还可以再创建主键,因为主键不一定需要是聚集的

23.临时表

--创建局部临时表
create table #newGrade
(
 classid int ,
 classname nvarchar(50)
)
---局部临时表只有在当前创建它的会话中使用,离开这个会话临时表就失效.如果关闭创建它的会话,那么临时表就会消失