sqlserver 阻止基于 IP 地址的访问

创建以下登录触发器，以阻止基于 IP 地址的访问，可能会遇到问题：

 CREATE TRIGGER tr_logon_CheckIP  
 ON ALL SERVER  
 FOR LOGON  
 AS
 BEGIN
  IF IS_SRVROLEMEMBER ( 'sysadmin' ) = 1  
     BEGIN
         DECLARE @IP NVARCHAR ( 15 );  
         SET @IP = ( SELECT EVENTDATA ().value ( '(/EVENT_INSTANCE/ClientHost)[1]' , 'NVARCHAR(15)' ));  
         IF NOT EXISTS( SELECT IP FROM DBAWork.dbo.ValidIP WHERE IP = @IP )  
         ROLLBACK ;  
     END ;  
 END ;  
 GO