Rails 4 where，order，group，count include zero's - postgresql [英] Rails 4 where,order,group,count include zero's - postgresql

问题描述

这是我的查询：

User.where("created_at >= ? AND created_at <=?", date1,date2).order('DATE(created_at) DESC').group("DATE(created_at)").count  

b $ b

，我输出为：

and I get output as:

{Thu, 15 May 2014=>1}  

但是我想在剩下的天数输出为0。例如

But I want to get output as 0 for the rest of the days. For ex

{Thu, 15 May 2014=>1,Fri, 15 May 2014=>0}  

我想得到的是 Users code>日期范围，已排序和分组由 created_at 和每天的用户的编号。当没有用户在某个特定的日子，它应该返回0，当前的查询不返回。

What I want to get is Users created in a date range, ordered and grouped by created_at and number of such Users for each day. When no users are there for a particular day it should return 0, which the current query doesn't return.

推荐答案

我同意 Himesh

尝试：

User.where("created_at >= ? AND created_at <=?", date1,date2).order('DATE(created_at) DESC').group("DATE(created_at)").count  

其中：

{Thu, 15 May 2014=>1}  

获取哈希初始化为0的日期范围：

Get the date range as hash initialized to 0:

hash1 = Hash[(date1..date2).collect { |v| [v, 0] }]  

现在合并两个哈希：

Now merge the two hashes:

hash = hash1.merge(hash) 

请记住将 hash 与 hash1 合并，而不是反之，因为我们要覆盖< $ 到 hash1

Do remember to merge hash with hash1 and not the vice-versa, because we want to overwrite the value of keys from hash to hash1

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