关于Case语句，请高手指点，急急急！！！

[mycenter1117]

有四张表Urge、OweDom_Sub、OweDom、RentContract,主要想实现当Urge.lMID=0时需要join OweDom_Sub，当Urge.lMID<>0时需要join OweDom，下面是我写的SQL语句，可是总是提示"在关键字 'case' 附近有语法错误。 "，不知道为什么？

select *
from Urge join
case Urge.lMID when 0 then ( OweDom_Sub on Urge.lSubID=OweDom_Sub.lID join RentContract on OweDom_Sub.sCntID=RentContract.sContractID)
else ( OweDom on Urge.lMID=OweDom.lID join RentContract on OweDom.sCntID=RentContract.sContractID)
end

[orcale]

寫成兩句再join

[yujohny]

case 不能这样用
必须改语句

[yujohny]

select * from Urge A join OweDom_Sub B on A.lSubID=B.lID
join RentContract C on B.sCntID=C.sContractID where A.lMID=0
union all
select *
from Urge D join OweDom E on D.lMID=E.lID join RentContract F on E.sCntID=F.sContractID
where D.lMID<>0

[zjcxc]

select *
from Urge join OweDom_Sub on Urge.lSubID=OweDom_Sub.lID and Urge.lMID=0
join OweDom on Urge.lMID=OweDom.lID where Urge.lMID<>0
join RentContract on OweDom.sCntID=RentContract.sContractID