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If you look at the table, some challenge_ids
s occur more than once. By using group by challenge_id the group function (sum) is only applied to those rows with the same challenge_id, thus giving the total submissions etc for the challenge with id challenge_id
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If you look at the table, some
challenge_id
s s occur more than once. By usinggroup by challenge_id
the group function (sum
) is only applied to those rows with the samechallenge_id
, thus giving the total submissions etc for the challenge with idchallenge_id