title: sql insert into self (copy existing rows) & increment foreign key
body: <p>I want to copy all existing rows in a table:   </p>
  
  <pre><code> INSERT INTO tbl (file_id, data) SELECT file_id, data FROM tbl
  </code></pre>
  
  <p>However I want to add a value to file_id so the inserted ones have an offset</p>