获取差集合的一种实现思路

select * from (
  select * from (
    select '1' from dual
    union all
    select '2' from dual
    union all
    select '3' from dual
    union all
    select '4' from dual
    union all
    select '5' from dual
  )
  minus
  select * from (
    select '155' from dual
    union all
    select '255' from dual
    union all
    select '455' from dual
    union all
    select '555' from dual
  )
)