Question

I have 2 models:

Subscriber
  - id
  - name:string
  - email:string

Submission
  - id
  - name:string
  - email:string
  - path:string
  - ip:string

They don’t have any relation.

I’d like to select all rows from subscribers and exclude rows with email address inserted in submission table where url equals ‘some/path’.

What is the most elegant way to do accomplish this with Rails?

Answer 1

I dont really get what you mean with: where url equals ‘some/path’
But i guess you can just add that as an extra condition…

if you solve it with a normal nested query you get:

 SELECT *  
 FROM subscribers 
 WHERE email NOT IN (Select email FROM Submission)

So in active record this would be:

 subscribers.all(:conditions => ["email NOT IN (SELECT email from Submission)"])

If you dont like to write that nested select query you can also do:

 emails = Submission.all
 subscribers.all(:conditions => ["email not in (?)", emails])

I didn’t test it, but it should be something along these lines.