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Hackerrank ollivander's inventory

I am practicing in hacker website. I searched the solution for problem in following link https://www.hackerrank.com/challenges/harry-potter-and-wands/problem I found the following solution ====== SELECT W.id, WP.age, W.coins_needed, W.power FROM Wands W INNER JOIN Wands_Property WP ON W.code = WP.code WHERE WP.is_evil != 1 AND W.coins_needed = ( SELECT MIN(W2.coins_needed) FROM Wands W2 INNER JOIN Wands_Property WP2 ON W2.code = WP.code WHERE WP2.age = WP.age AND W2.power = W.power) ORDER BY W.power DESC, WP.age DESC ======. But i don't know how the subquery works.pls explain me.

19th Mar 2022, 5:23 PM
Jawa - avatar
1 Answer
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Subquery works in a same way as outer query works. In this query you want to get that row which has minimum coins_needed value. So what you can do for that? First you can get minimum value of the column coins_needed then you can compare that minimum value in the same column coins_needed to get particular row. Here you are getting minimum value of coins_needed column from the table Wands and storing that value to a outer query in the same column coin_needed to get the row.
19th Mar 2022, 11:23 PM
A͢J - avatar