title: mongodb queries both with AND and OR
body: <p>can I use combination of OR and AND in mongodb queries?</p>
  
  <p>the code below doesn't work as expected</p>
  
  <pre><code>db.things.find({
             $and:[
                  {$or:[
                       {"first_name" : "john"}, 
                       {"last_name" : "john"}
                  ]},
                  {"phone": "12345678"}
              ]});
  </code></pre>
  
  <p><strong>database content:</strong></p>
  
  <pre><code>&gt; db.things.find();
  { "_id" : ObjectId("4fe8734ac27bc8be56947d60"), "first_name" : "john", "last_name" : "hersh", "phone" : "2222" }
  { "_id" : ObjectId("4fe8736dc27bc8be56947d61"), "first_name" : "john", "last_name" : "hersh", "phone" : "12345678" }
  { "_id" : ObjectId("4fe8737ec27bc8be56947d62"), "first_name" : "elton", "last_name" : "john", "phone" : "12345678" }
  { "_id" : ObjectId("4fe8738ac27bc8be56947d63"), "first_name" : "eltonush", "last_name" : "john", "phone" : "5555" }
  </code></pre>
  
  <p>when querying the above query - i get nothing!</p>
  
  <pre><code>&gt; db.things.find({$and:[{$or:[{"first_name" : "john"}, {"last_name" : "john"}]},{"phone": "12345678"}]});
  &gt;
  </code></pre>
  
  <p>I'm using mongo 1.8.3</p>