title: How to join values from multiple tables based on dates
body: <p>please assist with the following:
  I have 2 tables PurchaseO &amp; SalesO in database INFO.</p>
  
  <p>PurchaseO:</p>
  
  <pre><code>ITEMNO    DATE       QTY
  A         20180701   5
  A         20180702   2
  A         20180703   1
  B         20180701   2
  C         20180704   3
  </code></pre>
  
  <p>SalesO:</p>
  
  <pre><code>ITEMNO    DATE       QTY
  A         20180701   5
  A         20180704   4   
  B         20180702   2
  C         20180704   3
  </code></pre>
  
  <p>How can I join these two tables by DATE to get the following results:</p>
  
  <pre><code>ITEMNO    DATE       PurchaseQTY   SalesQTY
  A         20180701   5             5
  A         20180702   2
  A         20180703   1
  A         20180704                 4
  B         20180701   2
  B         20180702                 2
  C         20180704   3             3
  </code></pre>