title: sql concat when original field is empty
body: <p>I'm trying to run CONCAT on a column with fields that may or may not be empty. If the field isn't empty, there is no problem, i.e. if field in coulmn A equals a:</p>
  
  <pre><code>SET A = CONCAT(A, '_b')
  </code></pre>
  
  <p>gives a_b. The problem is, if the field in column A is empty, the concat returns nothing. Is there a way for it to concatenate even if the field is empty, which, in this example, would return '_b'?</p>