通过使用Rails 3个孩子的计数过滤器 [英] Filter by count of children using Rails 3

问题描述

我要选择具有使用Rails 3和一个查询一个或更多的评论文章。

I'd like to select posts that have one or more comments using Rails 3 and a single query.

我想是这样的：

Post.includes(:comments).where('count(comments.id)>0')

不过，我得到这个错误：

However I get this error:

ActiveRecord::StatementInvalid: PGError: ERROR:  aggregates not allowed in WHERE clause

我GOOGLE了这一点，类似的方法，按等，没有运气。任何帮助将AP preciated。

I've googled this and similar approaches, group by, etc with no luck. Any help will be appreciated.

推荐答案

我敢肯定，你可能已经想通了这一点了，但我相信你要找的是什么的有（：条件）的关系，何塞。

I'm sure you may have figured this out by now, but I believe what you're looking for is the having(:conditions) relationship, Jose.

Post.includes(:comments).having(:conditions => "count(comments.id) > 0")

我没有测试过code所以，请把它与一粒盐，但你一定要能够从那里跳开始。

I haven't tested that code so please take it with a grain of salt, but you should definitely be able to jump start from there.

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