title: Ruby Activerecord IN clause
body: <p>I was wondering if anyone knew how to do an "IN" clause in activerecord.  Unfortunately, the "IN" clause is pretty much un-googleable so I have to post here.  Basically I want to answer a question like this "Give me all the college students that are in these dormitories where the dormitory id is in this array [id array]".  I know how to write the query given a single dormitory id, but I don't know how to do it given an array of ids.</p>
  
  <p>Any help is greatly appreciated.  I'm sure this is a repost of a question somewhere, so I'll delete this once an answer/better search term is found.</p>