查询记录中没有记录的就返回空,否则返回原值

with ta as (

select '1' a from dual

union select '2' from dual  

 union select '3' from dual

)

select decode(count(*),0,'无','3') a from ta where a=3

 

第二种能够满足所有的信息记录

with a as (
     select '1' a,'b' b from dual
     union
     select '11' a,'bb' b from dual
     union
     select '111' a,'b' b from dual
)
--select COALESCE(NULL,2,3) from dual
select
r.c ,l.*
from
(select '1' c from dual) r,
--,(select a,b from a where a='11') l
(select '1' e,t.* from a t where t.a like '1111%' ) l
where r.c = l.e(+)