CODEWITHSUNDEEP
ruby-on-railsrubyactiverecordassociations
user2158382
user2158382

Reputation: 4520

Rails: ActiveRecord query based on association value

I have 2 models. Report and Server that have a belongs_to and has_many relationship. I created an accessor method using delegate that allows a Report to find its associated Server.company_id. Now, I want to run a query on Report that allows me to find all Report that are associated with a specific Server that has a specific company_id attribute of 5.

Here are my two models. And yes I know the current query wont work since Report does not have an attribute company_id.

And no, I dont want to store company_id inside of Report since that information doesn't belong in Report.

Report

class Report < ActiveRecord::Base

 belongs_to :server

 delegate :company_id, :to => :server

    class << self

        def method(url, base_url)
            #Report.where(company_id: 5)
        end
    end

end

Server

class Server < ActiveRecord::Base

 attr_accessible :company_id

 has_many :reports

end

Upvotes: 76

Views: 63742

Answers (4)

Sylar
Sylar

Reputation: 12092

This maybe an overkill but we have Arel:

# Get the SQL

# arelise will return the SQL (string)
def arelise(company_id)
    # Tables to query
    reports = Report.arel_table # Main table
    servers = Server.arel_table.alias('servers')

    reports
        .join(servers, Arel::Nodes::InnerJoin).on(reports[:server_id].eq(servers[:id]))
        .where(servers[:company_id].eq(company_id))
        # Select all (*)
        .project(reports[Arel.star])
        .to_sql
end

sql = arelise(1)
# puts sql

# To Execute:

reports = Report.find_by_sql(sql)

# puts reports

Upvotes: 0

KappaNossi
KappaNossi

Reputation: 2716

You can perform a query like this:

Report.joins(:servers).where(:servers => {:company_id => 5})

To me, this is the cleaner solution to raw SQL.

Upvotes: 110

Patrick Oscity
Patrick Oscity

Reputation: 54734

This should do the trick

Report.joins(:server).where('servers.company_id = ?', 5)

you could also add a scope for this like so

scope :with_company_id, lambda {|id| joins(:server).where('servers.company_id = ?', id) }

and then write

Report.with_company_id(5)

Upvotes: 27

Joseph Gill
Joseph Gill

Reputation: 1067

I'm using Rails 4.1.7 and the accepted answer did not work for me. What did work is 

Report.joins(:server).where(:servers => {:company_id => 5})

Note that the difference is the key in the where clause is pluralized (:servers instead of :server)

Upvotes: 49

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