title: If field is null, pull certain fields; otherwise, pull other fields
body: <p>I have the following table:</p>
  
  <pre><code>TestTable  
    ColumnA  
    Column1  
    Column2  
    Column3  
    Column4 
  </code></pre>
  
  <p>I want to write a simple SQL statement that checks ColumnA and depending on whether it is null or not returns certain columns.</p>
  
  <p>Something like (pseudo): </p>
  
  <pre><code>If ColumnA Is Null
    SELECT ColumnA, Column1, Column2 
    FROM TestTable
  Else
    SELECT ColumnA, Column3, Column4
    FROM TestTable
  </code></pre>
  
  <p>Any ideas?</p>