更新的动作你可以分2步理解，先delete ,再insert
所以，前的值在 deleted里
  后的值在 inserted里

create trigger t_ATDATEState_update
on list
for update
as
if update(ATDATEState)
begin
 declare @b_ATDATEState nvarchar(200)  --修改之前的
 declare @S_ATDATEState nVARCHAR(200)  --修改之后的
 declare @S_id INT
 
 SELECT @S_ATDATEState= ATDATEState FROM INSERTED --从更新后的副本表(临时表)里面 获得要修改后的状态
 
 select @S_id=id,@b_ATDATEState=ATDATEState from deleted  --从之前删掉的临时表里面获取原来的值
 
 if @S_ATDATEState is null
 begin
  set @S_ATDATEState='0'
 end
 if @b_ATDATEState is null
 begin
  set @b_ATDATEState='0'
 end
  --如果修改前为2，3,4  降低了状态 向下修改  并且 修改后的状态和修改前不一样 
 if ((convert(int,@b_ATDATEState)>=2  and convert(int,@S_ATDATEState)<convert(int,@b_ATDATEState)) and (@b_ATDATEState<>@S_ATDATEState))
  begin
   insert into dbo.operate(c_id,before_ATDATEState,after_ATDATEState,o_ip,o_type)
   values(@S_id,@b_ATDATEState,@S_ATDATEState,'','状态不正常,向下降低了')
  end
 if(convert(int,@b_ATDATEState)<2) and ( convert(int,@S_ATDATEState)>=2)
  begin
   insert into dbo.operate(c_id,before_ATDATEState,after_ATDATEState,o_ip,o_type)
   values(@S_id,@b_ATDATEState,@S_ATDATEState,'','状态升高')
  end
end