title: Multiple filters on SQL query
body: <p>I have been reading many topics about filtering SQL queries, but none seems to apply to my case, so I'm in need of a bit of help. I have the following data on a SQL table.</p>
  
  <pre><code>Date                    item     quantity moved   quantity in stock sequence
  
  13-03-2012 16:51:00    xpto         2                      2           1 
  13-03-2012 16:51:00    xpto        -2                      0           2
  21-03-2012 15:31:21    zyx          4                      6           1
  21-03-2012 16:20:11    zyx          6                      12          2
  22-03-2012 12:51:12    zyx         -3                      9           1
  </code></pre>
  
  <p>So this is quantities moved in the warehouse, and the problem is on the first two rows which was a reception and return at the same time, because I'm trying to make a query which gives me the stock at a given time of all items. I use <code>max(date)</code> but i don't get the right quantity on result.</p>