one way to consider
SELECT
A.Empid,
ISNULL(B.WeekoffChangeDate, A.WeekoffDate) AS ActualWeekOffDate
FROM Table_A AS A
LEFT OUTER JOIN Table_B AS B ON A.WeekoffDate = B.WeekoffDate
AND A.Empid = B.Empid
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you can lead a user to data....but you cannot make them think
and remember....every day is a school day