title: MySQL : Selecting alternative field if given field is empty
body: <p>I wonder if is it possible to run mysql command which can select an alternative field if the first given field is empty, on the same table.</p>
  
  <p>Example : I have table called "posts" which have "intro" and "content". In the same statement I would like to select as a result "content" if "intro" is empty, but not having both in the result array.</p>
  
  <p>Thanks in advance</p>