关于update中选择多表的问题

Question

下面这一段是sql server中的update语句，请问在oracle中如何更好的实现这个功能？
我目前是把其他的表的字段提前查询出来，写到变量里面，在用变量来判断，感觉太复杂了，也不好维护，特来找一个更好的方法
    update t1
       set t1.FteamNo       = t2.FNewteamNo       ,
           t1.Fstatus       = t2.FNewstatus       ,
           t1.FStartWorkSeg = t2.FNewStartWorkSeg ,
           t1.FStartProp    = t2.FNewStartProp    ,
           t1.FEndWorkSeg   = t2.FNewEndWorkSeg   , 
           t1.FEndProp      = t2.FNewEndProp      
      from t_HREmpMonthly t1 , Inserted t2 ,t_hradjustteam  t3 
     where t1.FEntityNo   = t2.FEntityNo and
           t1.FEmpNo      = t2.FEmpNo    and
           t2.Fentityno   = t3.Fentityno and
           t2.FbillNo     = t3.FbillNo   and
           t3.FStatus     = 'A'          and
          (t1.FDate between t2.FfromDate and t2.FToDate)

Answer 1

update t1
       set (t1.FteamNo,
           t1.Fstatus,
           t1.FStartWorkSeg ,
           t1.FStartProp,
           t1.FEndWorkSeg, 
           t1.FEndProp)=(
select      
t2.FNewteamNo,
t2.FNewstatus,
t2.FNewStartWorkSeg,
t2.FNewStartProp,
t2.FNewEndWorkSeg,
t2.FNewEndProp 
      from Inserted t2 ,t_hradjustteam  t3 
     where t1.FEntityNo   = t2.FEntityNo and
           t1.FEmpNo      = t2.FEmpNo    and
           t2.Fentityno   = t3.Fentityno and
           t2.FbillNo     = t3.FbillNo   and
           t3.FStatus     = 'A'          and
          (t1.FDate between t2.FfromDate and t2.FToDate)
)
where exists(
select      
t2.FNewteamNo,
t2.FNewstatus,
t2.FNewStartWorkSeg,
t2.FNewStartProp,
t2.FNewEndWorkSeg,
t2.FNewEndProp 
      from Inserted t2 ,t_hradjustteam  t3 
     where t1.FEntityNo   = t2.FEntityNo and
           t1.FEmpNo      = t2.FEmpNo    and
           t2.Fentityno   = t3.Fentityno and
           t2.FbillNo     = t3.FbillNo   and
           t3.FStatus     = 'A'          and
          (t1.FDate between t2.FfromDate and t2.FToDate)
)

Answer 2

update 
    t1
set 
   (t1.FteamNo,
    t1.Fstatus,
    t1.FStartWorkSeg ,
    t1.FStartProp,
    t1.FEndWorkSeg, 
    t1.FEndProp)=(select      
                      t2.FNewteamNo,
                      t2.FNewstatus,
                      t2.FNewStartWorkSeg,
                      t2.FNewStartProp,
                      t2.FNewEndWorkSeg,
                      t2.FNewEndProp 
                  from 
                      Inserted        t2 ,
                      t_hradjustteam  t3 
                  where 
                      t1.FEntityNo   = t2.FEntityNo 
                      and
                      t1.FEmpNo      = t2.FEmpNo    
                      and
                      t2.Fentityno   = t3.Fentityno 
                      and
                      t2.FbillNo     = t3.FbillNo   
                      and
                      t3.FStatus     = 'A'          
                      and
                      (t1.FDate between t2.FfromDate and t2.FToDate))
where 
    exists(select      
               1 
           from 
               Inserted        t2 ,
               t_hradjustteam  t3 
           where 
               t1.FEntityNo   = t2.FEntityNo 
               and
               t1.FEmpNo      = t2.FEmpNo    
               and
               t2.Fentityno   = t3.Fentityno 
               and
               t2.FbillNo     = t3.FbillNo   
               and
               t3.FStatus     = 'A'          
               and
               (t1.FDate between t2.FfromDate and t2.FToDate))

Answer 3

where exists(
select      
t2.FNewteamNo,
t2.FNewstatus,
t2.FNewStartWorkSeg,
t2.FNewStartProp,
t2.FNewEndWorkSeg,
t2.FNewEndProp 
      from Inserted t2 ,t_hradjustteam  t3 
在这一段里面，select部分是不是不能变，还是可以随便替换？例如
where exists(
select 1  from Inserted t2 ,t_hradjustteam  t3