I have a table of orders, there are two types of orders. "fix" and "new". All orders have an orderDate. I need to order the results of a mysql select in an unusual way.

If the order is type "fix", it will have a due date of the order date PLUS 1 day.

If the order is type "new", it will have a due date of the order date PLUS 2 days.

I need to order by the due date, but the due date is something that does not exist in a column. How can I do this?