title: How do you do many to many table outer joins?
body: <p>I have 3 tables, foo, foo2bar, and bar.  foo2bar is a many to many map between foo and bar.  Here are the contents.</p>
  
  <pre><code>select * from foo
  +------+
  | fid  |
  +------+
  |    1 |
  |    2 |
  |    3 |
  |    4 |
  +------+
  
  select * from foo2bar
  +------+------+
  | fid  | bid  |
  +------+------+
  |    1 |    1 |
  |    1 |    2 |
  |    2 |    1 |
  |    2 |    3 |
  |    4 |    4 |
  +------+------+
  
  select * from bar
  +------+-------+------+
  | bid  | value | zid  |
  +------+-------+------+
  |    1 |     2 |   10 |
  |    2 |     4 |   20 |
  |    3 |     8 |   30 |
  |    4 |    42 |   30 |
  +------+-------+------+
  </code></pre>
  
  <p>What I want to request is, "Give me a list of all the fid and values with zid of 30"</p>
  
  <p>I expect an answer for all the fids, so the result would look like:</p>
  
  <pre><code>+------+--------+
  | fid  | value  |
  +------+--------+
  |    1 |   null |
  |    2 |      8 |
  |    3 |   null |
  |    4 |     42 |
  +------+--------+
  </code></pre>