title: Why would empty results be shown when using IS NOT NULL?
body: <p>I'm using the below code however empty results are shown even when using <code>IS NOT NULL</code>.</p>
  
  <pre><code>SELECT COLUMN1
         ,COLUMN2
         ,COLUMN3
      FROM TABLE.DBF
      WHERE COLUMN1 IS NOT NULL
      ORDER BY COLUMN1 ASC
  </code></pre>
  
  <p>Example result:</p>
  
  <pre><code>     50 0
       51 0
       50 0
       51 0
       50 0
       51 0
  1    50 35000
  1    51 29334.71
  10   50 10000
  10   51 1568.14
  100  50 25000
  100  51 -2731.98
  </code></pre>
  
  <p>If I switch this to <code>&gt; 0</code> then the empty results are not shown. Ideally <code>IS NOT NULL</code> would be better to use as it makes more sense. How can I make it work? There is <strong>nothing</strong> in that column for that row.</p>
  
  <p>Example result using <code>&gt; 0</code> instead of <code>IS NOT NULL</code>:</p>
  
  <pre><code>1    50 35000
  1    51 29334.71
  10   50 10000
  10   51 1568.14
  100  50 25000
  100  51 -2731.98
  </code></pre>