[英]Rails Join With Association and Count
所以我有以下...
我想要的是列出具有相關提供者數量的大學,但提供者還需要一個地址。
我嘗試過的
@universities = University.joins(:providers).select('universities.id, universities.name, universities.slug, providers.id, count(providers.id) as count').group('universities.id').order('count').reverse
提供如下列表:
- id: 14
name: Salus University
slug: salus-university
count: 72
- id: 22
name: University of Florida
slug: university-of-florida
count: 45
問題是計數包括沒有地址的提供程序。 所以我嘗試了以下方法:
@universities = University.joins(providers: :addresses).select('universities.id, universities.name, universities.slug, providers.id, count(providers.id) as count').group('universities.id').order('count').reverse
但是,這給了我地址總數的計數,而不是地址提供者的計數:
- id: 14
name: Salus University
slug: salus-university
count: 90
- id: 22
name: University of Florida
slug: university-of-florida
count: 60
好的,我終於弄清楚了。 我只是加入了職位,並增加了distinct
的數量:
@universities = University.joins(providers: :positions).select('universities.id, universities.name, universities.slug, providers.id, count(distinct providers.id) as count').group('universities.id').order('count desc')
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