title: check if column exists before ALTER TABLE -- mysql
body: <p>Is there a way to check if a column exists in a mySQL DB prior to (or as) the <code>ALTER TABLE ADD coumn_name</code> statement runs? Sort of an <code>IF column DOES NOT EXIST ALTER TABLE</code> thing.</p>
  
  <p>I've tried <code>ALTER IGNORE TABLE my_table ADD my_column</code> but this still throws the error if the column I'm adding already exists.</p>
  
  <p>EDIT: use case is to upgrade a table in an already installed web app-- so to keep things simple, I want to make sure the columns I need exist, and if they don't, add them using <code>ALTER TABLE</code></p>