title: mongodb equivalent for MYSQL concat()
body: <p>I would like to search the <code>user</code> collection by <code>first_name</code> and <code>last_name</code> keyed in as <code>full_name</code> in the search query. The search query for the <code>full_name</code> would be the <code>first_name</code> separated by a 'blank space', followed by the <code>last_name</code>. Both <code>first_name</code> and <code>last_name</code> may have blank spaces. In mysql I would do this something like</p>
  
  <pre><code>SELECT * FROM users WHERE(CONCAT(users.first_name, users.last_name) == 'Peter Griffin')
  </code></pre>
  
  <p>NOTE: I'm using <code>mongo -v 2.2.0</code> and I thought that <a href="http://docs.mongodb.org/manual/reference/aggregation/concat/" rel="nofollow">concat</a> could work, but I could not test it since <code>2.2.0</code> doesn't support the concat function</p>
  
  <p>Is there a way to achieve the above query in mongodb?</p>