title: Store UUID v4 in MySQL
body: <p>I'm generating UUIDs using PHP, per the function found <a href="https://stackoverflow.com/a/15875555/339440">here</a></p>
  
  <p>Now I want to store that in a MySQL database.  What is the best/most efficient MySQL field format for storing UUID v4?</p>
  
  <p>I currently have varchar(256), but I'm pretty sure that's much larger than necessary.  I've found lots of almost-answers, but they're generally ambiguous about what form of UUID they're referring to, so I'm asking for the specific format.</p>