Question

我的数据看起来像这样

 ___________________________________
|name  date      status    location |
|Tom   1/1/2010  Ready     Home     |
|Tom   1/1/2010  Ready     Home     |
|Bill  1/18/2010 Go        Work     |
|Bob   2/19/2010 Ready     Field    |
|Bob   2/19/2010 Ready     Field    |
|Wil   4/5/2010  Steady    Work     |
|Wil   4/5/2010  Steady    Work     |
|Wil   4/5/2010  Steady    Work     |
|Wil   4/5/2010  Steady    Home     |
|Bill  7/14/2010 Stop      Home     |
|___________________________________|

我需要对它进行分组/计数，使其看起来像这样

Name   Date      Location    Status   Count
Tom    1/1/2010  Home        Ready    2
Bill   1/18/2010 Work        Go       1
Bill   7/14/2010 Home        Stop     1
Bob    2/19/2010 Field       Ready    2
etc.....

Answer 1

根据数据的格式和属性，有时最好的方法是棘手的。但一般来说，您可以使用ActiveRecord#find的:group参数。

Model.all(:select => 'COUNT(*) AS count, name, date, location, status', :group => 'name')

或者如果使用Rails 3

Model.all.select('COUNT(*) AS count, name, date, location, status').group('name')

如果您始终打算根据此关系对数据进行分组，请考虑将其作为默认范围添加到模型中。

class Model < ActiveRecord::Base
  default_scope select('COUNT(*) AS count, name, date, location, status')
  default_scope group('name')
end

轨道中的多列分组和总计

1 个答案: