title: Fetching Minimum/Maximum for each group in ActiveRecord
body: <p>This is an age-old question where given a table with attributes 'type', 'variety' and 'price', that you fetch the record with the minimum price for each type there is.</p>
  
  <p>In SQL, we can do <a href="http://www.xaprb.com/blog/2006/12/07/how-to-select-the-firstleastmax-row-per-group-in-sql/" rel="noreferrer">this</a> by:</p>
  
  <pre><code>select f.type, f.variety, f.price   
  from (  select type, min(price) as minprice from table group by type ) as x  
  inner join table as f on f.type = x.type and f.price = x.minprice;`
  </code></pre>
  
  <p>We could perhaps imitate this by:</p>
  
  <pre><code>minprices = Table.minimum(:price, :group =&gt; type)  
  result = []
  minprices.each_pair do |t, p|  
     result &lt;&lt; Table.find(:first, :conditions =&gt; ["type = ? and price = ?", t, p])
  end
  </code></pre>
  
  <p>Is there a better implementation than this?</p>