How do you do a Rails 3 select IN using where clauses

Question

I am using Rails 3 and I need to do a select where the primary key of the records is IN a resulting previous select. You can do this easily using straight SQL using an IN. Here is the obviously incorrect way I have done what I need. What's the Rails way to do this well:

@task = Link.find(params[:id]) clients = Client.where('task_id = ?',@task.id).select('DISTINCT(company_id)') company_list = [] clients.each do |client|   company_ids << client.company_id end @companies = Company.where(:id => company_ids) 

Answer 1

As others have mentioned I'd use join in this case. The syntax for using "in" is also very simple though e.g.

company_ids = [1,2,3,4] @companies = Company.where("id in (?)", company_ids) 

Update

Actually it's even simpler than that now (I think rails 3+), you can do

company_ids = [1,2,3,4] @companies = Company.where(id: company_ids) 

Answer 2

This does not answer your question about "select IN using where clauses", but I think your whole script can be rewritten in one line using joins. This should give the same result as your snippet above:

@companies = Company.joins(:clients).where(:clients => {:task_id => params[:id]})