Like left join, right join selects all the observations from the right dataset and the matched records from the left table.
PROC SQL;
CREATE TABLE C AS
SELECT A.*, B.CC_NUMBER, B.START_DATE
FROM CUSTOMER A RIGHT JOIN CC_DETAILS B
ON A.CUSTOMERID=B.CUSTOMERID
QUIT;
Dataset C contains all the values from the right table, plus matched values from the left table or missing values in the case of no match.