title: sql join syntax
body: <p>I'm kind of new to writing sql and I have a question about joins.  Here's an example select:</p>
  
  <pre><code>select bb.name from big_box bb, middle_box mb, little_box lb
  where lb.color = 'green' and lb.parent_box = mb and mb.parent_box = bb;
  </code></pre>
  
  <p>So let's say that I'm looking for the names of all the big boxes that have nested somewhere inside them a little box that's green.  If I understand correctly, the above syntax is another way of getting the same results that we could get by using the 'join' keyword.</p>
  
  <p>Questions: is the above select statement efficient for the task it's doing?  If not, what is a better way to do it?  Is the statement syntactic sugar for a join or is it actually doing something else?  </p>
  
  <p>If you have links to any good material on the subject I'd gladly read it, but since I don't know exactly what this technique is called I'm having trouble googling it.</p>