Question

我在t-sql中执行一个触发器，它会在每个INSERT，UPDATE或DELETE语句之后使'budget'表保持最新状态。要在预算表中插入信息，我使用：

INSERT INTO budget (value) SELECT SUM(sal) FROM emp

我每次删除表只保留1条记录（我想在触发器上做同样的事情。

这是我的触发器的代码：

DROP TRIGGER licznik
go
CREATE TRIGGER licznik ON emp
    FOR INSERT, UPDATE, DELETE
AS
    DELETE  FROM budget
    DECLARE @sal_new INT ,
        @sal_old INT
    SELECT  @sal_new = sal
    FROM    inserted
    SELECT  @sal_old = sal
    FROM    deleted
    PRINT @sal_new
    IF @sal_new > 0 
        BEGIN
            UPDATE  budget
            SET     value = value + @sal_new
        END
    IF @sal_old > 0 
        BEGIN
            UPDATE  budget
            SET     value = value - @sal_old
        END
    SET @sal_new = 0
    SET @sal_old = 0

触发器不应该从开始计算整个预算，而是根据EMP表中的更改来增加或减少预算 - 这就是我更新行的原因。不幸的是它根本不起作用。

如何解决这个问题？

Answer 1

create view BudgetView as

SELECT SUM(sal) FROM emp

除非emp只是令人兴奋，否则观点会很快这些触发器给emp增加了很多开销

Answer 2

这将处理设定的操作并相应地更新预算：

create trigger licznik on emp
for insert, update, delete
as
-- Make sure that there is a budget row to update.
if not exists ( select 42 from Budget )
  insert into Budget ( Value ) values ( 0 );
-- Get the total of the adjustments.
declare @DeletedSum as Int;
declare @InsertedSum as Int;
select @DeletedSum = sum( Sal ) from deleted;
select @InsertedSum = sum( Sal ) from inserted;
-- Update the budget.
update Budget
  set Value += Coalesce( @InsertedSum, 0 ) - Coalesce( @DeletedSum, 0 );

如何添加到现有行？

2 个答案: