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

Symmetric Pairs

  • metinsenturk
     + 1 comment

    Thanks to @szavgorodni, I realized we should also consider the count of equals. Commenting rocks!

    select a.x, a.y from (
    -- tuples with not equals that follow the rule
    select f1.x, f1.y 
    from functions f1 join functions f2 
    on (f1.x = f2.y and f2.x = f1.y and (f1.x != f1.y))
    and f1.x < f1.y
    union
    -- tuples with the equals that follow the rule
    select f1.x, f1.y 
    from functions f1 join functions f2 
    on (f1.x = f2.y and f2.x = f1.y and (f1.x = f1.y))
    group by f1.x,f1.y
    having count(1) > 1
) a
order by a.x asc