Question

我在想。我有这个Trigger，它完全符合我的要求。

      USE [IGOR]
      GO
      /****** Object:  Trigger [dbo].[AfterInsertTarget]    Script Date: 11/20/2013 14:46:06 ******/
      SET ANSI_NULLS ON
      GO
      SET QUOTED_IDENTIFIER ON
      GO


      ALTER TRIGGER [dbo].[AfterInsertTarget] ON  [dbo].[DMM_TARGET] 

      after insert 
      as 
      set nocount on 

      update DMM_TARGET 
      set ID_WEEK = 0 
      WHERE FREQ = 'Daily'

我的问题是：如果仅在插入的行上FREQ ='Daily'，更新语句是否将ID_WEEK设置为0？或者它是否通过整个表循环？因为现在它只有50000个条目。但是，如果它变得像数百万，那么由于触发器，只需要一段时间才能插入一行。

Answer 1

您的触发器当前更新所有行，因为与inserted伪表没有关联，伪表只包含触发器调用所涉及的记录。仅影响新行：

ALTER TRIGGER [dbo].[AfterInsertTarget] 
ON [dbo].[DMM_TARGET] 
AFTER INSERT
AS
BEGIN
  SET NOCOUNT ON;

  UPDATE t SET ID_WEEK = 0
    FROM dbo.DMM_TARGET AS t
    WHERE EXISTS (SELECT 1 FROM inserted WHERE key = t.key);
END
GO

或者：

ALTER TRIGGER [dbo].[AfterInsertTarget] 
ON [dbo].[DMM_TARGET] 
AFTER INSERT
AS
BEGIN
  SET NOCOUNT ON;

  UPDATE t SET ID_WEEK = 0
    FROM dbo.DMM_TARGET AS t
    INNER JOIN inserted AS i
    ON t.key = t.key;
END
GO

但是，在ID_WEEK列上创建默认约束要容易得多。

插入触发器后的SQLServer，它是遍历整个表还是仅插入行。

1 个答案: