Count values with mysql queries

Let’s say you have the following table called bill that keeps track hours of people who are billable and non billable  and you want a query to count the number of hours for you instead of having to loop through all the rows with a counter in PHP

(0= non bill hours , 1= bill hours)

Work_id	Bill	Hours
1	0	10
2	0	4
3	0	5
1	1	3
2	1	2

The sql to do this is

SELECT work_id , sum(IF(bill=1, (hours), 0)) AS Bill_hours, sum(IF(bill=0, (hours), 0)) AS Non_bill_hours FROM `work` GROUP BY work_id

Work_id	Bill_hours	Non_bill_hours
1	3	10
2	2	4
3	0	5