关于事务，存储过程，触发器的简单例子

用一个简单的Bank表分别对事务，存储过程和触发器写个简单例子

Bank表有连个字段：Id（账号）varchar(4);

　　　　　　　　　　Balance(账号金额）money （check约束 Balance>10)

1.事务（转账）

 1 begin transaction

 2 declare @error int;

 3 set @error=0;

 4 update bank set Balance=Balance-1000 where Id='0001';

 5 set @error=@error+@@ERROR;

 6 update bank set Balance=Balance+1000 where Id='0002';

 7 set @error=@error+@@ERROR;

 8 if @error>0

 9 begin

10  rollback transaction

11 end

12 else

13 begin

14  commit transaction

15 end

使用try-catch）(减少代码量）

begin transaction

begin try

 update bank set Balance=Balance-1000 where Id='0001';

 update bank set Balance=Balance+1000 where Id='0002';

 commit transaction

end try

begin catch

 rollback transaction

end catch

2存储过程（转账）

alter proc usp_MoveBalance

@cash money,

@inBankId char(4),

@OutBankId char(4),

@currentCash money output,  --显示余额

@flag bit output            --是否转成功

as

begin

begin transaction

 begin try

  update bank set Balance=Balance-@cash where Id=@OutBankId;

  update bank set Balance=Balance+@cash where Id=@InBankId;

  set @flag=1;

  commit transaction 

 end try

 begin catch

  set @flag=0;

  rollback transaction

 end catch 

 select @currentCash=Balance from bank where Id=@OutBankId;

end



--执行存储过程



declare @flag bit;

declare @currentCash money;

exec usp_MoveBalance 100,'0002','0001',@currentCash output,@flag output

select @flag

select @currentCash

3.触发器-（如果给任何账户打钱，都会把钱打到'0004'这个账号）（instead of)还有另一种触发器after（写for默认是after）

create trigger TriBankUpdate on bank

instead of Update

as

begin

 declare @afterUpdateCash money;

 declare @beforeUpdateCash money;

 declare @cash money;

 select @afterUpdateCash=Balance from inserted;

 select @beforeUpdateCash=Balance from deleted;

 set @cash=@afterUpdateCash-@beforeUpdateCash;

 if @cash>0

 begin

  Update bank set Balance=Balance+@cash where Id='0004';

 end

end



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--测试



select * from bank



update bank set Balance=Balance+1000 where Id='0001';