title: Generate GUID in MySQL for existing Data?
body: <p>I've just imported a bunch of data to a MySQL table and I have a column "GUID" that I want to basically fill down all existing rows with new and unique random GUID's.</p>
  
  <p>How do I do this in MySQL ?</p>
  
  <p>I tried</p>
  
  <pre><code>UPDATE db.tablename
    SET columnID = UUID()
    where columnID is not null
  </code></pre>
  
  <p>And just get every field the same</p>