Question

在Rails中，我想在页面上显示每天“创建”有多少新“用户”。

在常规SQL中，我会做类似的事情：

SELECT 
DATE(created_at) as day,
COUNT(1) as new_user_count
FROM users
WHERE created_at > '2014-01-01 01:01:01'
GROUP BY day

如何针对Rails中的Users表执行此操作？同样，我需要在页面上显示这个，所以我不是在PG GUI上寻找指令。

具体来说，我正在使用Heroku和Postgres。

Answer 1

这样做：

sql = "SELECT DATE(created_at) as day, COUNT(1) as new_user_count " \
      "FROM users WHERE created_at > '2014-01-01 01:01:01' " \
      "GROUP BY day"

ActiveRecord::Base.connection.execute(sql)

Answer 2

除了原始SQL解决方案之外，您可以考虑创建一个视图：

create view daily_user_counts as
SELECT 
  DATE(created_at) as day,
  COUNT(*) as new_user_count
FROM users
WHERE created_at > '2014-01-01 01:01:01'
GROUP BY day;

...并为其创建只读模型：

class DailyUserCount < ActiveRecord::Base

  def readonly?
    true
  end

end

然后：

DailyUserCount.where("day > ? ", from).order(:day)

如何对Postgres运行任意SQL

2 个答案: