title: Convert varchar column to date in mysql at database level
body: <p>I have one column <code>date1</code> which is <em>varchar</em> type
  I want this column to <code>date</code> type.
  I tried changing field but all date is converted to <code>0000-00-00</code>.
  format is <code>dd-mm-yyyy</code> but in <em>varchar</em>.</p>
  
  <p>How can I convert the same date format but with date format using sql queries or similar but at database level ?</p>