2 テーブルの差分を MySQL で。

diff.sql

select 
  'a dake' as type
, id
, ckey 
from 
  table_a a 
where not exists
  (select 1 from table_b b where a.id <=> b.id and a.ckey <=> b.ckey)
union all
select 
  'b dake' as type
, id
, ckey
from
  table_b b
where not exists
  (select 1 from table_a a where b.id <=> a.id and b.ckey <=> a.ckey)
;