title: How to add more rows to a table/dataframe with increasing dates to a certain date for all value of another column
body: <p>I have a table of all countries and their daily record of covid 19 vaccinations. Some countries have records till April 27, 2021, but many do not. So the date columns stop at earlier than April 27 for those countries. My question is how do I add more rows under each country with the date increasing till April 27. Other values can be null. I prefer using Python and SQL. Thank you!</p>
  <p><img src="https://i.stack.imgur.com/Nw3dp.png" alt="image" /></p>