title: sql select based on column in another table
body: <p>Ok I have two tables.</p>
  
  <p>One table is called Persons and just has columns Pname and Age. (A person's name and their age).
  Another table is called Giving and has donor, receiver, and giftname.  (donor and receiver have foreign key constraints referencing persons.pname).</p>
  
  <p>I need to find the names of all people who donated a gift to someone with a different age.</p>