title: Replace null values with the former row's value
body: <p>Have a table with Exchange rates, but some days have null values. For the days with null values, i want to pick the earlier day's exchange rate. Any help?</p>
  
  <p><a href="https://i.stack.imgur.com/YfLsg.png" rel="nofollow noreferrer">Exchange rate Table</a></p>