[MySQL/해커랭크] Symmetric Pairs

www.hackerrank.com/challenges/symmetric-pairs/problem Symmetric Pairs | HackerRank Write a query to output all symmetric pairs in ascending order by the value of X. www.hackerrank.com JOIN을 이용한 간단한 문제입니다. 문제의 조건은 X1 = Y2 && X2 = Y1 이여야 합니다. select f1.x, f1.y from functions f1 join functions f2 on (f1.x = f2.y and f2.x = f1.y) group by f1.x, f1.y having count(*) > 1 or f1.x < f1.y order by f1.x