Hackerrank SQL Solutions | Challenges SQL Hackerrank Intermediate Problem

Published: 25 April 2021
on channel: The Coding Mentor

19,953

392

In this video I am solving the "Challenges" Problem on Hackerrank. This is an intermediate SQL Problem.
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0:00 Introduction
0:20 Problem Solving Approach
01:09 Problem Description
01:27 Outline Output
03:01 Sample Input Description
5:25 Start solving first Part
9:32 Include With Statement
11:30 Combine tables to get result
14:05 Where Clause
16:12 Order By

Query:

With tbl_num_challenges as (

SELECT
h.hacker_id,
h.name,
COUNT(c.challenge_id) as num_challenges
FROM Hackers h
JOIN Challenges c ON c.hacker_id = h.hacker_id
GROUP BY h.hacker_id, h.name
--ORDER BY COUNT(c.challenge_id) desc, hacker_id asc

)

,tbl_count_challenges as (
SELECT
num_challenges,
COUNT(num_challenges) as count_challenges
FROM tbl_num_challenges
GROUP BY num_challenges
--ORDER BY COUNT(num_challenges) desc

)

SELECT
tnc.hacker_id,
tnc.name,
tnc.num_challenges--,
--tcc.count_challenges
FROM tbl_num_challenges tnc
JOIN tbl_count_challenges tcc ON tcc.num_challenges = tnc.num_challenges
WHERE tcc.count_challenges = 1
OR
tnc.num_challenges = (SELECT max(num_challenges) FROM tbl_num_challenges)

ORDER BY
tnc.num_challenges desc,
tnc.hacker_id
;

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