title: change only the month of a date in sql
body: <p>i have a column <code>readiness_dt</code> which is a date in <code>mm/dd/yyyy</code> .I want to update the month of this date to the value present in another column <code>month</code>. Is there a query to just modify the month for a date.<br>
  E.g. readiness_dt      month
        02/14/2013       06<br>
  I want a function which should change the readiness_dt  to 06/14/2013</p>