Return Column Names Where Values Were Not Found [stored Procedure]

I need to check whether procedure found any matches or not. If not it has to return the column name where matching value was not found. For example, if there was no record found in the table "Addresses" column "customer" with the value @username, it should return "street". If id with value @prod_id was not found in the table "Products", the "productname" must be returned as well.

CREATE PROC sp_test
@id INT,
@username VARCHAR(50),
@prod_id INT
AS

SELECT name FROM Customers WHERE id=@id
SELECT street FROM Addresses WHERE customer=@username
SELECT productname FROM Products WHERE id=@prod_id


It is kind of check, which has to find out if users have inserted all the necessary values or not.
Thanks for any advice.