55

Challenge 55 - 15 days of learning SQL

Julia conducted a $15$ days of learning SQL contest. The start date of the contest was March 01, 2016 and the end date was March 15, 2016.

Write a query to print total number of unique hackers who made at least $1$ submission each day (starting on the first day of the contest), and find the hacker_id and name of the hacker who made maximum number of submissions each day. If more than one such hacker has a maximum number of submissions, print the lowest hacker_id. The query should print this information for each day of the contest, sorted by the date.

The Hackers table is described as follows:

Column	Type
hacker_id	Integer
name	String

The hacker_id is the id of the hacker, and name is the name of the hacker.

The Submissions table is described as follows:

Column	Type
submission_date	Date
submission_id	Integer
hacker_id	Integer
score	Integer

The submission_date is the date of the submission, submission_id is the id of the submission, hacker_id is the id of the hacker who made the submission, and score is the score of the submission.

Solutions

• Microsoft SQL Server