如何查找属于多个模型对象的模型对象

Question

Suppose I have the models Book and Reading, which has the relationship Book has_many :readings. 假设我有Book and Reading模型，它与Book has_many：readings关系。

Now suppose I want to find all books that have been read in the past week. 现在，假设我想查找过去一周中已阅读的所有书籍。 I know I can find readings created in the past week with something like: readings = Reading.find(:all, :conditions => ["created_at > ?", Date.today - 7]) 我知道我可以找到上周创建的读数，例如：读数= Reading.find（：all，：conditions => [“ created_at>？”，Date.today-7]）

However, I'm not sure how to get from that list of readings to a de-duplicated list of books. 但是，我不确定如何从阅读清单到重复数据删除的书籍清单。 I know I can't simply do readings.books because readings is an array and Array#books is not defined. 我知道我不能简单地做readings.books，因为读数是一个数组，而Array＃books没有定义。

Any help would be appreciated. 任何帮助，将不胜感激。

Answer 1

Book.joins(:readings).group(:book_id).having("COUNT(*) > 1")

如何查找属于多个模型对象的模型对象

问题描述

1 个解决方案

解决方案1
0 2011-12-15 22:29:22

如何查找属于多个模型对象的模型对象

问题描述

1 个解决方案

解决方案1 0 2011-12-15 22:29:22

解决方案1
0 2011-12-15 22:29:22