title: Pulling field depending on date?
body: <p>I am trying to use a <code>select</code> statement to get specific fields from a database.  However, in my data the field-mapping changed on a specific date.</p>
  
  <p>Is it possible for me to write something like a <code>CASE</code> expression to select one field if the date-column is before date <code>X</code> and another field on date <code>Y</code> and combine them in the same column?</p>