Hackerrank SQL Challenges

challenge.sql

/*
 Julia asked her students to create some coding challenges. Write a query to print the hacker_id, name, and the total number of challenges created by each student. Sort your results by the total number of challenges in descending order. If more than one student created the same number of challenges, then sort the result by hacker_id. If more than one student created the same number of challenges and the count is less than the maximum number of challenges created, then exclude those students from the result.
 */
with count_table as (
    select
        h.hacker_id,
        h.name,
        count(*) challenge_count
    from
        challenges c
        join hackers h on c.hacker_id = h.hacker_id
    group by
        h.hacker_id,
        h.name
)
select
    hacker_id,
    name,
    challenge_count
from
    count_table
where
    challenge_count in (
        select
            challenge_count
        from
            count_table
        group by
            challenge_count
        having
            count(challenge_count) <= 1
    )
    or challenge_count = (
        select
            max(challenge_count)
        from
            count_table
    )
order by
    challenge_count desc,
    hacker_id;