Data that does not match any existing model?

How about a MusicVideo.count_by_date method?

def self.count_by_date

select [date, count] rows

dates_and_counts = connection.select_all(COUNT_BY_DATE_SQL)

transform to { date => count, … } hash

dates_and_counts.group_by { |row| row.first }

You can probably do it with calculations API - worth taking a look - but hacking out the SQL this way is fine too.