Rails加入协会和计数

Question

So I have the following...

• University - has many providers
• Provider - belongs to university, and has many addresses through positions
• Position - belongs to provider and address
• Address - has many providers through positions

What I want is a list of universities with associated provider count but the providers also need an address.

What I have tried:

@universities = University.joins(:providers).select('universities.id, universities.name, universities.slug, providers.id, count(providers.id) as count').group('universities.id').order('count').reverse

Provides a list like:

- id: 14
  name: Salus University
  slug: salus-university
  count: 72
- id: 22
  name: University of Florida
  slug: university-of-florida
  count: 45

The problem is the count includes providers with no address. So I tried the following:

@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

However, this gives me the count of the total number of addresses instead of providers with addresses:

- id: 14
  name: Salus University
  slug: salus-university
  count: 90
- id: 22
  name: University of Florida
  slug: university-of-florida
  count: 60

Answer 1

OK, I managed to figure this out finally. I just joined with positions and added distinct to the count:

@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')