触发器变量的申明


CREATE TRIGGER ManagerUser_Triggers 
ON ManagerUser
 FOR INSERT,DELETE,UPDATEASIF EXISTS(SELECT * FROM INSERTED)
IF NOT EXISTS(SELECT * FROM DELETED)
BEGIN DECLARE @UserID AS int
DECLARE @UserName AS varchar(20)
DECLARE @UserPassword AS varchar(10)
DECLARE @UserSort AS varchar(10) SELECT @UserID = UserID,
@UserName = UserName,
@UserPassword = UserPassword,
@UserSort = UserSort
FROM INSERTED   

INSERT INTO [ManagerUser_History]
(UserID,
UserName,
UserPassword,
UserSort,
[TimeStamp],
TypeOfChange)
VALUES
(@UserID,
@UserName,
@UserPassword,
@UserSort,
GETDATE(),
'insert') END
ELSE 
BEGIN INSERT INTO [ManagerUser_History]
(UserID,
UserName,
UserPassword,
UserSort,
[TimeStamp],
TypeOfChange) SELECT  UserID,
UserName,
UserPassword,
UserSort,
GETDATE(),
'update'
FROM inserted    END
ELSE
BEGIN INSERT INTO [ManagerUser_History]
(UserID,
UserName,
UserPassword,
UserSort,
[TimeStamp],
TypeOfChange) SELECT UserID,
UserName,
UserPassword,
UserSort,
GETDATE(),
'delete' 
FROM deleted END------------------------------------------------------------
CREATE TRIGGER ManagerUser_Triggers ON ManagerUserFOR INSERT , DELETE ,UPDATEASIF EXISTS(SELECT * FROM INSERTED)
   IF NOT EXISTS(SELECT * FROM DELETED)
  
   BEGIN
   INSERT INTO ManagerUser_History SELECT  
                UserID,
UserName,
UserPassword,
UserSort,
GETDATE(),
'INSERT'
FROM INSERTED   END
ELSE
  BEGIN
 INSERT INTO ManagerUser_History SELECT  
                UserID,
UserName,
UserPassword,
UserSort,
GETDATE(),
'UPDATE'
FROM INSERTED  END
ELSE
BEGIN
INSERT INTO ManagerUser_History SELECT  UserID,
UserName,
UserPassword,
UserSort,
GETDATE(),
'DELETE'
FROM DELETED    END以上是具有相同功能（至少面前再应用的时候没发现不同）的两个触发器 我想知道 申明看变量和不申明变量的区别是什么