Symmetric Pairs in SQL | HackerRank Solution

Hello coders, today we are going to solve Symmetric Pairs HackerRank Solution in SQL.

Symmetric Pairs

Contents

Problem

You are given a table, Functions, containing two columns: and Y.

ColumnType
XInteger
YInteger

Two pairs (X1, Y1) and (X2, Y2) are said to be symmetric pairs if X1 = Y2 and X2 = Y1.

Write a query to output all such symmetric pairs in ascending order by the value of X. List the rows such that X1 ≤ Y1.

Sample Input

XY
2020
2020
2021
2322
2223
2120

Sample Output

20 20
20 21
22 23

Solution – Symmetric Pairs in SQL

MySQL

SELECT X,
       Y
FROM FUNCTIONS F1
WHERE EXISTS
    (SELECT *
     FROM FUNCTIONS F2
     WHERE F2.Y = F1.X
       AND F2.X = F1.Y
       AND F2.X > F1.X)
  AND (X != Y)
UNION
SELECT X,
       Y
FROM FUNCTIONS F1
WHERE X = Y
  AND (
         (SELECT COUNT(*)
          FROM FUNCTIONS
          WHERE X = F1.X
            AND Y = F1.X) > 1)
ORDER BY X;

Disclaimer: The above Problem (Symmetric Pairs) is generated by Hacker Rank but the Solution is Provided by CodingBroz. This tutorial is only for Educational and Learning Purpose.

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