在Rails中进行分组和计数 [英] Group and count in Rails

问题描述

我知道我以前见过，但现在找不到任何东西。我想按某个列对查询进行分组，并能够显示每个组中有多少个查询。我把第一部分记下来：

I know I've seen this before but I can't find anything now. I want to group a query by a certain column and be able to display how many are in each group. I got the first part down:

@line_items = @project.line_items.all(:group => "device_id")  

这是我的订单项索引视图，它只是一个显示订单项的表格。既然订单项已按设备分组，如何在该表中为计数创建一列？

This is for my line item index view, which is just a table displaying the line items. How do I make a column in that table for "count" now that the line items are grouped by device?

推荐答案

您可以在 line_items 上执行 count ，这将返回 device_id 和 count 。

You can do count on line_items which will return you an ordered hash of device_id and count.

@project.line_items.group(:device_id).count

这篇关于在Rails中进行分组和计数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！