SQL 触发器 疑问

CREATE TRIGGER [dbo].[update_shouliaolist]

ON [dbo].[shouliaolist]

FOR UPDATE --插入触发

AS

    -- 先更新再插入，避免插入后再更新一次



    UPDATE Log

       SET sl = sl + inserted.sl

      FROM Log, inserted

     WHERE Log.wuliaohao = inserted.wuliaohao

       AND inserted.chufaqi = '1'



    INSERT INTO Log

    SELECT wuliaohao, sl

      FROM inserted

     WHERE chufaqi = '1'

       AND NOT EXISTS(SELECT *

                        FROM Log

                       WHERE Log.wuliaohao = inserted.wuliaohao)

CREATE TRIGGER [dbo].[update_shouliaolist]
ON dbo.ShouLiaoList 
AFTER INSERT
AS
BEGIN

	--更新后的数据
	SELECT 
		wuliaohao,
		SUM(sl) AS sl 
	INTO 
		#UpdList
	FROM 
		Inserted
	GROUP BY 
		wuliaohao

	UPDATE 
		aa
	SET 
		aa.sl = aa.sl + b.sl
	FROM 
		[log] aa INNER JOIN #UpdList b ON aa.wuliaohao = b.wuliaohao

	INSERT dbo.log( 
		wuliaohao, sl )
	SELECT 
		wuliaohao, sl
	FROM 
		#UpdList a
	WHERE 
		NOT EXISTS( SELECT * FROM log b WHERE a.wuliaohao = b.wuliaohao )

END
GO