title: get the SUM between two given dates
body: <p>if i want to get the total_consumption over a range of dates, how would i do that?</p>
  
  <p>I thought i could do:</p>
  
  <pre><code>SELECT id, SUM(consumption) 
  FROM consumption_info 
  WHERE date_time BETWEEN 2013-09-15 AND 2013-09-16 
  GROUP BY id;
  </code></pre>
  
  <p>however this returns: Empty set, 2 warnings(0.00 sec)</p>
  
  <pre><code>---------------------------------------
  id | consumption |  date_time          |        
  =======================================|
  1  |      5      | 2013-09-15 21:35:03 |
  2  |      5      | 2013-09-15 24:35:03 |
  3  |      7      | 2013-09-16 11:25:23 |
  4  |      3      | 2013-09-16 20:15:23 |
  ----------------------------------------
  </code></pre>
  
  <p>any ideas what i'm doing wrong here?</p>
  
  <p>thanks in advance</p>