如何获得两个表中的行数之间的差异？

select (select count(1) from A) - (select count(1) from B) from dual

如果MINUS你真的需要它，那么你可以

select count(*) from
(
  select rownum from a 
  minus 
  select rownum from b
)

但如果 A 中的行数较少，则此查询将返回 0。

毕竟，如果还需要负差异，那么你可以做这样的事情

select sum(cnt) from
(
  select count(*) cnt from
  (
    select rownum from a 
    minus 
    select rownum from b
  )
  union
  select count(*) *-1 from
  (
    select rownum from b 
    minus 
    select rownum from a
  )
)