title: Update statement SQL to increment date by 365 days
body: <p>I have two columns in my mysql db, end_date (example 9999-12-31) and start_date (example 2010-11-17), of type "DATE".</p>
  
  <p>I want to do an update statement on the table such that if end_date = 9999-12-31, It will change the end_date to start_date + 365 days. But I only want it do update if end_date is 9999-12-31 (which essentially means no end date has been set)</p>