title: How to return NULL when result is empty?
body: <p>I have a simple query that selects one field and only one row, thus one value.</p>
  
  <p>Is there any way to make it return NULL if the query results in an empty set? Instead of returning zero rows?</p>
  
  <p>I think I need to use something with NOT EXISTS, THEN NULL but not certain about it.</p>