title: Select column, if blank select from another
body: <p>How does one detect whether a field is blank (not null) and then select another field if it is?</p>
  
  <p>What I really need is a IsBlank function that works the same as IsNull but with with blanks.</p>
  
  <p>REPLACE doesn't work with blanks, COALESCE only works with NULLS.</p>