2012.6.19.sql不常用函数总结，以及事务，增加，删除触发器

distinct 删除重复行

declare @x 申明一个变量

convert(varchar(20),tscore.tenglish) 类型转换

cast(xx as varchar(10)) 类型转换

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情况

case

when xxx then xx

when xxxx then xxxxx

else

end

=======================================================

while xxx

begin

xxxxxx

end

事务

===================================================

begin tran

declare @sum int = 0

update bank set balance=balance-1000 where cid='0001'

set @sum=@sum+@@error

update bank set balance=balance + 1000 where cid='0002'

set @sum=@sum+@@error

if @sum<>0

begin

rollback

print '回滚！'

end

else

begin

--提交事务

commit tran

print '提交了！'

end

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begin tran

begin try

declare @sum int = 0

update bank set balance=balance-900 where cid='0001'

set @sum=@sum+@@error

update bank set balance=balance + 900 where cid='0002'

set @sum=@sum+@@error

commit

end try

begin catch

rollback

end catch

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declare @halfCount int= ceiling(@count/2.0) 向上

增加时触发器

=========================================

create trigger tri_TblClass_insert_after

on TblClass after insert

as

begin

declare @id int

declare @name varchar(50)

declare @desc varchar(50)

select @id=tclassId,@name=tclassname,@desc=tclassdesc from inserted

print @id

print @name

print @desc

end

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删除时触发器

create trigger tri_TblClass_delete_after

on TblClass instead of delete

as

begin

insert into TblClassBak

select * from deleted

end

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