title: Obtain null values of result from a query
body: <p>I have this query:</p>
  
  <pre><code>SELECT U.LOCATION,SUM(S.EXISTENCIA) AS Total
  FROM LOCATIONS U
  LEFT JOIN CANT_WAREHOUSE S ON U.LOCATION= S.LOCATION
  WHERE U.ENABLED= 1 
  GROUP BY U.LOCATION
  </code></pre>
  
  <p>And return data like this:</p>
  
  <pre><code>LOCATION  | Total
  2A-1      | 566.0000000
  2A-2      | 14.0000000
  2A-3      | 1.0000000
  2A-4      | (null)
  2A-5      | 1.0000000
  2A-6      | (null)
  2A-7      | 6.0000000
  2B-1      | 560.0000000
  2B-2      | (null)
  </code></pre>
  
  <p>Is there a way to get the 'LOCATION' with 'TOTAL' = null using subquery or something like that? </p>