PG组错误

Question

想要将我的表格与created_at日期，user_id，action和trackable_type分组。

但是按照查询分组不能为PG工作并给出错误。

PG::GroupingError: ERROR: column "activities.id" must appear in the GROUP BY...

activities = Activity.all.group("activities.created_at::date, activities.user_id, activities.action, activities.trackable_type")

因此按功能将activities.id添加到组

activities = Activity.all.group("activities.created_at::date, activities.user_id, activities.action, activities.trackable_type, activities.id")

给出了puts "#{activities.map{|a| a.id}}"

的结果

[645, 646, 642, 643, 644]

正确的结果应该是

1 => [645, 646, 642], 2 => [643, 644]

使用：

ruby​​ 1.9.3

rails 3.2.6

0.14.0

Answer 1

您可以尝试使用select列表来缩小查询范围，然后您不需要将activities.id添加到GROUP BY子句中。

标准SQL要求SELECT子句中的所有项都要聚合或包含在GROUP BY子句中。默认情况下，Rails在ActiveRecord查询中执行SELECT *，然后强制您在GROUP BY中包含所有字段。限制SELECT列表字段可能会有所帮助。

试试这个：

activities = Activity.all
               .select(:created_at, :user_id, :action, :trackable_type)
               .group("activities.created_at::date, activities.user_id, activities.action, activities.trackable_type")