SQL group by date, but get dates w/o records too

Question

Is there an easy way to do a GROUP BY DATE(timestamp) that includes all days in a period of time, regardless of whether there are any records associated with th

Answer 1

Assuming you have more orders than dates something like this could work:

select date, count(id) as orders
from
(
  SELECT DATE_ADD('2008-01-01', INTERVAL @rn:=@rn+1 DAY) as date from (select @rn:=-1)t, `order` limit 365
) d left outer join `order` using (date)
group by date