title: SQL select distinct exclude NULL rows
body: <p>SQL query:</p>
  <pre class="lang-sql prettyprint-override"><code>SELECT DISTINCT [File Version Number], [Enrollment Employee ID] 
  FROM Participant
  </code></pre>
  <p>Result:</p>
  <pre class="lang-sql prettyprint-override"><code>+---------------------+------------------------+
  | Fule Version Number | Enrollment Employee ID |
  +---------------------+------------------------+
  | null                | null                   |
  | null                | 1100527                |
  | null                | 5032506                |
  | v2.2.0              | null                   |
  +---------------------+------------------------+
  </code></pre>
  <p>Desired result: exclude rows with NULL data; the FIRST row.</p>
  <p>I understand we can use where clause on both columns to filter null rows but what if we have large number of columns to select, and we don't want to have long <code>where</code> clause?</p>
  <p>Any solution or workaround would be highly appreciated. Thanks.</p>