Write a query to which returns a table with name and remember$\_$token, if remember$\_$token is not there, then return password$\_$digest.

Tables Schema as Below:

USERS

columnName dataType

id INT

username VARCHAR$(50)$

email VARCHAR$(50)$

remember$\_$token VARCHAR$(50)$

created$\_$at DATETIME

updated$\_$at DATETIME

password$\_$digest VARCHAR$(50)$