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  1. Prepare
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  4. 15 Days of Learning SQL
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15 Days of Learning SQL

  • fengli97
     + 15 comments

    the problem description not clear , waste me alot time

    select 
submission_date ,

( SELECT COUNT(distinct hacker_id)  
 FROM Submissions s2  
 WHERE s2.submission_date = s1.submission_date AND    (SELECT COUNT(distinct s3.submission_date) FROM      Submissions s3 WHERE s3.hacker_id = s2.hacker_id AND s3.submission_date < s1.submission_date) = dateDIFF(s1.submission_date , '2016-03-01')) ,

(select hacker_id  from submissions s2 where s2.submission_date = s1.submission_date 
group by hacker_id order by count(submission_id) desc , hacker_id limit 1) as shit,
(select name from hackers where hacker_id = shit)
from 
(select distinct submission_date from submissions) s1
group by submission_date