Just to clarify, you can still get the same results without normalizing the
DaysOff table... :)
SELECT E.emp_id,
C.date
FROM DaysOff AS E, CalendarDays AS C
WHERE C.date BETWEEN @start and @end
AND NOT EXISTS
(SELECT *
FROM DaysOff AS O
WHERE O.emp_id = E.emp_id
AND C.calendar_dow IN (O.dayoff_1, O.dayoff_2));