禁止sa 远程登录，只允许sa这个用户可以在本机登录

如果连接的ip不是指定ip，则rollback
CREATE TRIGGER connection_limit_trigger
ON ALL SERVER
FOR LOGON
AS
BEGIN
 declare @ip nvarchar(max)
 declare @loginName nvarchar(max)
 SELECT @ip=EVENTDATA().value
        ('(/EVENT_INSTANCE/ClientHost)[1]','nvarchar(max)')
    SELECT @loginName=EVENTDATA().value
        ('(/EVENT_INSTANCE/LoginName)[1]','nvarchar(max)')
    if @loginName='sa' and @ip<>'127.0.0.1'--replaced with your ip
      rollback
END;