rails 3 group by date datetime列 [英] rails 3 group by date a datetime column
本文介绍了rails 3 group by date datetime列的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我如何按日期分组? start_at列是一个datetime列
解决方案
这应该工作(rails 3):
Foo.order(:start_at).group(DATE(start_at))。count
编辑:如果您使用PostgreSQL,查询应该是
Foo.order(DATE(start_at))。group(DATE(start_at))。count
或者您将收到错误
(PGError:ERROR:columnfoos.start_at必须出现在GROUP BY子句或用于聚合函数)
根据
和
http://www.pastbedti。我/ 2009/11 / g rouping-a-timestamp-field-by-date-in-ruby-on-rails-postgresql /
Foo.group(:start_at).count(:id)
How I can group this by date ? the "start_at" column is an datetime column
解决方案
This should work (rails 3):
Foo.order(:start_at).group("DATE(start_at)").count
edit: if you're using PostgreSQL, the query should be
Foo.order("DATE(start_at)").group("DATE(start_at)").count
or you'll get an error
("PGError: ERROR: column "foos.start_at" must appear in the GROUP BY clause or be used in an aggregate function")
Based on
Graphing new users by date in a Rails app using Seer
and
http://www.pastbedti.me/2009/11/grouping-a-timestamp-field-by-date-in-ruby-on-rails-postgresql/
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