Этот запрос должен работать, попробуйте.
DECLARE @DME TABLE
(
Useruid int,
UserFullName varchar(200),
NonWorkHrs int,
VacationHours int,
TimeEntered int
)
INSERT INTO @DME
VALUES
(1,'Jane Doe',18,8,-8),
(1,'Jane Doe',18,0,10),
(1,'Jane Doe',18,0,12),
(2,'John Doe',18,18,-18),
(2,'John Doe',18,0,23),
(3,'Bob Builder',18,16,-16),
(3,'Bob Builder',18,0,40)
SELECT d.* FROM @DME d
UPDATE @DME
SET NonWorkHrs = T2.VacationHours
FROM @DME T1
INNER JOIN (SELECT Max(VacationHours) AS VacationHours, Useruid FROM @DME GROUP BY Useruid) AS T2
ON T2.Useruid = T1.Useruid
SELECT d.* FROM @DME d