ruby-on-rails - rails 3 group by 和 sum

Question

我有以下模型:

activity_types: id, name

activities: id, id_activity_type, occurrences, date (other fields)

事件表存储事件每天发生的次数。但现在我想向用户显示每个月发生的每种类型的事件数量。

我得到了以下解决方案 based on this post这似乎没问题:

Activity.all(:joins => :activity_types,
             :select => "activity_types.id, activity_types.name, SUM(activities.occurrences) as occurrences",
             :group => "activity_types.id, activity_types.name",
             :order => "activity_types.id")

但这似乎有很多 Rails 标准和 rails API says it's deprecated 的代码.

我发现以下解决方案非常简单:

Activity.sum(:occurrences).group(:activity_type_id)

它返回一个带有 的哈希值事件类型 ID => 出现。

我该怎么做才能获得以下哈希值: 事件类型名称 => 出现？

Answer 1

如果原始查询有效，那么只需尝试使用 Rails 3 语法重写它:

Activity.joins(:activity_types)
  .select("activity_types.id, activity_types.name, SUM(activities.occurrences) as occurrences")
  .group("activity_types.id, activity_types.name")
  .order("activity_types.id")