Rails 中的多表查询

Question

I have done simple Rails finds for two tables, but now find that with a 4 table query I am not making good progress. All tables are connected with keys and are basically:

• User (has many)
• Phones (has many)
• Campaigns (has many)
• Calls

I just want to count the total number of calls a specific user has and the total number of calls for a specific campaign. I could also add user-id to Campaigns and Calls but for some reason I think that cheating or a bad idea. I just don't know.

Answer 1

Rails 3:

Total number of calls a specific user has:

@user.phones.joins(:campaigns => :calls).count

Total number of calls for a specific campaign:

@user.phones.joins(:campaigns => :calls).where('campaigns.id' => @campaign.id).count

Answer 2

Assuming that a phone belongs to a user, and a campaign belongs to a phone:

# total calls for a specific campaign
campaign_call_count = Campaign.find(id).calls.count
# or a report for all campaings
Campaign.all.map{|c| "#{c.name}: #{c.calls.count}"

#total calls a user has
user_phone_ids = user.phones.map(&:id)
user_calls_by_campaign = Campaign.where(:phone_id=>user_phone_ids).map{|campaign| "#{user.name} calls for #{campaign.name}: #{campaign.calls.count}" }
puts user_calls_by_campaign

That should give you a list