SQL Tigger 如何區分Insert, Update, Delete

ALTER TRIGGER [dbo].[TRI_TableName]

     ON  [dbo].[TableName]

     AFTER INSERT,DELETE,UPDATE

AS

BEGIN

 SET NOCOUNT ON;

 DECLARE @action as char(1);

 SET @action = 'I'; -- Set Action to Insert by default.

 IF EXISTS(SELECT * FROM DELETED)

    BEGIN

        SET @action =

            CASE

                WHEN EXISTS(SELECT * FROM INSERTED) THEN 'U' -- Set Action to Updated.

                ELSE 'D' -- Set Action to Deleted.      

            END

    END

if @action = 'I'

     begin

         -- 新增 Insert

     end

if @action = 'U'

     begin

         -- 修改 Update

     end

if @action = 'D'

     begin

         -- 刪除 Delete

     end

END