title: Using CASE statement with isnull and else
body: <p>I have a column <code>Color</code> which contains <code>Black</code>, <code>Red</code>, <code>NULL</code>, <code>WW</code>, <code>RR</code>.</p>
  <p>I want a column which has</p>
  <pre><code>if color black then 'B'
  if color red then 'r'
  if color is Null then 'Empty'
  for all other entries 'n/a'
  </code></pre>
  <p>I'm using the following, but it throws an error:</p>
  <pre><code>SELECT Name,
          CASE color
              WHEN 'black' THEN 'b'
              WHEN 'red' THEN 'r'
              WHEN ISNULL(color, 'empty')
              else 'n/a'
             END AS Color_code
  FROM SalesLT.Product;
  </code></pre>