title: mysql how to update a table by auto-incrementing a column
body: <p>A MySql 5.3 table with 100K rows has a primary key. </p>
  
  <p>There is also an integer column which is not part of the key. I would like to update this column to contain a unique number for the table. E.g. for the first record it should contain 1, for the second 2 etc. </p>
  
  <p>This could as well be an auto-increment column, but MySql does not allow auto-increment on non-key columns. I don't want this column to be part of the key, because of the way it gets populated from a file etc. </p>
  
  <p>So how such a query would look like?</p>