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  1. Prepare
  2. SQL
  3. Advanced Join
  4. Symmetric Pairs
  5. Discussions

Symmetric Pairs

  • szavgorodni
     + 1 comment
    /*
I think this is a bit easier to understand 
for somebody who prefers joins over exists 
*/
select
    t.x
  , t.y
from (
  select
      a.x
    , a.y
    -- , b.x as xi
    -- , b.y as yi
  from functions a
    inner join functions b
      on a.x = b.y
         and a.y = b.x
         and a.x < a.y
  union
  select
      x
    , y
    -- , count(*)
  from functions a
  where 1=1
    and x=y
  group by
    x,y
  having count(*) > 1
) t
order by
   t.x
  ,t.y
;