Ruby-on-rails 如何按天而不是按日期分组？
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How do I group by day instead of date?
提问by Matt Elhotiby
ok so i have
好的，所以我有
>> list = Request.find_all_by_artist("someBand")
=> [#<Request id: 1, artist: "someBand", song: "someSong", venue: "Knebworth - Stevenage, United Kingdom", showdate: "2011-07-01", amount: nil, user_id: 2, created_at: "2011-01-01 18:14:08", updated_at: "2011-01-01 18:14:09".............
and then
进而
list.group_by(&:created_at).map {|k,v| [k, v.length]}.sort
=> [[Sat, 01 Jan 2011 18:14:08 UTC +00:00, 10], [Sun, 09 Jan 2011 18:34:19 UTC +00:00, 1], [Sun, 09 Jan 2011 18:38:48 UTC +00:00, 1], [Sun, 09 Jan 2011 18:51:10 UTC +00:00, 1], [Sun, 09 Jan 2011 18:52:30 UTC +00:00, 1], [Thu, 10 Feb 2011 02:22:08 UTC +00:00, 1], [Thu, 10 Feb 2011 20:02:20 UTC +00:00, 1]]
the problem is I have a few Sun, 09 Jan and a couple for the 10th, instead of one like this
问题是我有几个星期日，1 月 9 日和一对夫妇在 10 日，而不是这样的
this is what i need
这就是我需要的
=> [[Sat, 01 Jan 2011 18:14:08 UTC +00:00, 10], [Sun, 09 Jan 2011 18:34:19 UTC +00:00, 4], [Thu, 10 Feb 2011 20:02:20 UTC +00:00, 2]]
回答by Simone Carletti
Timeis a quite complex object to group by. Assuming you want to group by the creation date, instead of the full Time, start creating a custom method in your model to return the group criteria.
Time是一个非常复杂的分组对象。假设您想按创建日期而不是 full 进行分组Time，请开始在模型中创建自定义方法以返回组条件。
The method should return the creation date, possibly as string.
该方法应该返回创建日期，可能是字符串。
def group_by_criteria
created_at.to_date.to_s(:db)
end
Then, group by that method.
然后，按该方法分组。
list.group_by(&:group_by_criteria).map {|k,v| [k, v.length]}.sort
回答by Fellps
I think this is a much more elegant and simple solution
我认为这是一个更优雅和简单的解决方案
list.group_by{|x| x.created_at.strftime("%Y-%m-%d")}
回答by laffuste
回答by you786
Ipsum's answer is actually good and probably the best:
Ipsum 的答案实际上很好，而且可能是最好的：
In Arel:
在阿雷尔：
requests = Arel::Table.new(:requests)
query = requests.project("COUNT(*), CAST(requests.created_at AS DATE) as created_at")
query = query.group("CAST (requests.created_at AS DATE)")
Request.find_by_sql(query.to_sql)
回答by Abel
Group without extra gems:
没有额外宝石的组：
def self.group_by_day items
data = items.group_by{|x| x.created_at.to_date}
chart_data = {}
data.each do |a,b|
chart_data.merge!({a => b.count})
end
return chart_data
end
回答by Ibrahim Saifee
you can use GROUP BY DATE(created_at)in MySQL
你可以GROUP BY DATE(created_at)在 MySQL 中使用
On ruby code you can use like this
在 ruby 代码上，您可以像这样使用
list.group('DATE(created_at)').map {|k,v| [k, v.length]}.sort
