use pubs
go

create table log_jobs
(job_id int, newval int,oldval int,date1 datetime)

go

create trigger kkkk  on jobs
for update 
as
begin
   declare @value int
   select @value=(select count(*) from log_jobs where job_id in (select job_id from deleted))
      if @value=0 
         begin
       insert into log_jobs
           select a.job_id,a.min_lvl,b.min_lvl,getdate()
           from deleted a join inserted b
           on a.job_id=b.job_id
         end
      else
         begin
           update log_jobs
           set newval=b.min_lvl,oldval=a.min_lvl,date1=getdate()
           from deleted a  join inserted b
           on a.job_id=b.job_id
           where log_jobs.job_id=a.job_id
         end   
 
end


update jobs 
set min_lvl=180
where job_id=2

select * from log_jobs

/*
job_id      newval      oldval      date1                                                  
----------- ----------- ----------- ------------------------------------------------------ 
1           200         100         2007-11-15 17:10:30.153
2           180         200         2007-11-15 17:11:37.153

（所影响的行数为 2 行）
*/

------解决方案--------------------
对于多用户的情况,你可以这样实现
当有用户使用这个公共表时你可以先创建一个事物,然后用TABLOCKX把这个表锁定
在这个用户使用完后再用commit来结束事物
这样就OK了