Demo, Sql Server - rextester

Language: Layout:

CREATE TABLE #temp
    ([emplyID] int, [hours] int, [projID] int, [date] datetime)
;
    
INSERT INTO #temp
    ([emplyID], [hours], [projID], [date])
VALUES
    (2, 3, 5, '2015-01-01 00:00:00'),
    (5, 5, 5, '2015-03-02 00:00:00'),
    (3, 4, 5, '2015-06-02 00:00:00'),
    (9, 3, 5, '2015-05-03 00:00:00'),
    (2, 3, 5, '2015-01-01 00:00:00'),
    (5, 5, 5, '2015-02-02 00:00:00'),
    (3, 4, 5, '2015-06-02 00:00:00'),
    (9, 3, 5, '2015-06-03 00:00:00')
;

CREATE TABLE workHours
    ([emplyID] int, [hours] int, [projID] int, [date] datetime)
;
    
INSERT INTO workHours
    ([emplyID], [hours], [projID], [date])
VALUES
    (3, 4, 5, '2015-06-02 00:00:00'),
    (9, 3, 5, '2015-06-03 00:00:00'),
    (2, 3, 5, '2015-01-01 00:00:00'),
    (5, 5, 5, '2015-02-02 00:00:00'),
    (2, 3, 5, '2015-01-01 00:00:00'),
    (5, 5, 5, '2015-02-02 00:00:00'),
    (3, 4, 5, '2015-06-02 00:00:00'),
    (9, 3, 5, '2015-06-03 00:00:00')
;

select emplyID,sum(totalHours)
From
(
select emplyID, 
       hours as totalHours
from workHours as a 
union all
select emplyID, 
       hours as totalHours
From #temp as b
) a
Group by emplyID

View schema
Execution time: 0,03 sec, rows selected: 4, rows affected: 16, absolute service time: 0,19 sec