How to do this query

hi all, i am trouble with this query requirement.
Suppose i have the two tables:
administrator:
+--------+-------------+--------+
| emp_id | name | gender |
+--------+-------------+--------+
| 20001 | Kate Tse | F |
| 20002 | John Cheung | M |
| 20003 | Kevin Cheng | M |
| 20004 | Richard | M |
+--------+-------------+--------+

adm_work_hours:
+--------+------------+-------+
| emp_id | day | hours |
+--------+------------+-------+
| 20001 | 2004-01-10 | 2.50 |
| 20001 | 2004-01-11 | 2.00 |
| 20002 | 2004-01-10 | 3.00 |
| 20002 | 2004-01-11 | 3.50 |
| 20003 | 2004-01-10 | 8.00 |
+--------+------------+-------+

i need to write a query that find the total working hours
of every administrators. Here is my written query:

SELECT R.emp_id, R.name, sum(hours) as Total_Hours
FROM Administrator as R, Adm_work_hours as S
WHERE R.emp_id = S.emp_id
GROUP BY R.emp_id, R.name
ORDER BY Total_Hours ;


However, I cannot get the work hours of Richard
(emp_id=20004) as 0. How can I also show that his working
hours is zero in the result?


thanks

Query that might work. I'm pretty sure it's the LEFT JOIN....

SELECT R.emp_id, R.name, sum(hours) as Total_Hours
FROM Administrator as R LEFT JOIN Adm_work_hours as S on ( R.emp_id = S.emp_id )
GROUP BY R.emp_id, R.name
ORDER BY Total_Hours