触发器捕获批量修改

　　最近在批量更新数据时，发现无论怎么操作触发器都仅仅捕获到了一条数据，触发器代码大致如下。

ALTER TRIGGER [dbo].[Trigger_Demo_Update]
   ON  [dbo].[B_Demo_TB]
   AFTER UPDATE
AS
BEGIN
    SET NOCOUNT ON;
    DECLARE @NewData INT,@OldData INT;

    SELECT @OldData=Data FROM DELETED

    SELECT @NewData=Data FROM INSERTED

        IF(@OldData!=@NewData)
        BEGIN
            INSERT INTO M_TriggleSoft(Data)
            VALUES(@NewData)
        END

END

我们知道在触发器中DELETE和INSERTED其实是两张虚表，因此用变量获取仅能得到一条数据，但是如果用游标的话可以获取到位于虚表中的所有数据，批量处理。于是修改如下：

ALTER TRIGGER [dbo].[Trigger_Demo_Update]
   ON  [dbo].[B_Demo_TB]
   AFTER UPDATE
AS
BEGIN
    SET NOCOUNT ON;
    DECLARE @NewData INT,@OldData INT;

    DECLARE cursorDel CURSOR FOR SELECT Data FROM DELETED

    DECLARE cursorINSERT CURSOR FOR SELECT Data FROM INSERTED

    open cursorDel
    open cursorINSERT

    FETCH NEXT FROM cursorDel INTO @OldData

    FETCH NEXT FROM cursorINSERT INTO @NewData

    WHILE @@FETCH_STATUS=0
        BEGIN
            IF(@OldData!=@NewData)
            BEGIN
                INSERT INTO M_TriggleSoft(Data)
                VALUES(@NewData)
            END
            FETCH NEXT FROM cursorDel INTO @OldData

            FETCH NEXT FROM cursorINSERT INTO @NewData
         END
    CLOSE cursorDel
    DEALLOCATE cursorDel
    CLOSE cursorINSERT
    DEALLOCATE cursorINSERT
END

既然明白了触发器中DELETE和INSERTED是两张虚表，那么其实上述的操作也可以这么来:

ALTER TRIGGER [dbo].[Trigger_Demo_Update]
   ON  [dbo].[B_Demo_TB]
   AFTER UPDATE
AS
BEGIN
    SET NOCOUNT ON;
    DECLARE @NewData INT,@OldData INT;

    SELECT @OldData=Data FROM DELETED

    SELECT @NewData=Data FROM INSERTED

            INSERT INTO M_TriggleSoft(DATA) SELECT Data FROM INSERTED INNER JOIN DELETED ON INSERTED.ID=DELETED.ID WHERE INSERTED.DATA=DELETED.DATA
        END

END