SQL Interview Questions – Find Interview Candidates

Problem Description –

Write an SQL query to report the name and the mail of all interview candidates. A user is an interview candidate if at least one of these two conditions is true:

• The user won any medal in three or more consecutive contests.
• The user won the gold medal in three or more different contests (not necessarily consecutive).

Return the result table in any order.

The query result format is in the following example.

Problem Link – Find interview candidates

Difficulty Level – Medium

Solution –

with t0 as (
    select gold_medal as user, contest_id 
    from contests 
    union all 
    select silver_medal as user, contest_id 
    from contests 
    union all 
    select bronze_medal as user, contest_id 
    from contests 
)
, t1 as (
    select user, contest_id, row_number() over(partition by user order by contest_id) as rn 
    from t0 
)
, t2 as (
    select user as user_id -- consecutive medal winners
    from t1 
    group by user, contest_id - rn 
    having count(*) >= 3 -- replace 3 with any number to solve the N problem
    union all
    select gold_medal as user_id  -- gold medal winners
    from contests 
    group by gold_medal 
    having count(*) >= 3
)
select distinct u.name, u.mail 
from t2 
inner join users u
on t2.user_id = u.user_id