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

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

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

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

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


作者 xhccom