sql,DATE,group by

想要計算某些column 每天的總數時, 可以用sql 的DATE<br />#select 出這個月份每天的render 數<br />>> Render.count(:all, :conditions => {:created_at => Time.now.beginning_of_month..Time.now}, :group => 'DATE(created_at)')<br /><br />SELECT count(*) AS count_all, DATE(created_at) AS date_created_at FROM `renders` WHERE (`renders`.`created_at` BETWEEN '2008-12-01 00:00:00' AND '2008-12-17 16:09:20') GROUP BY DATE(created_at)<br /><br />=> [["2008-12-16", 1], ["2008-12-17", 24]]<br />
結果出來是 OrderedHash 所以要用
hash["2008-12-16"] 去取值, 當然hash 的相關method 也可以用