mysql total working hours

id     title                              start                    end
1   Doing Coding for this project.  2013-04-02 02:00:00     2013-04-02 04:00:00
2   Doing Coding for this project.  2013-04-02 04:00:00     2013-04-02 06:00:00
3   Doing Coding for this project.  2013-04-02 06:00:00     2013-04-02 06:30:00

I have above MySQL database table record. Now i want to get the total number of hours.

I am developing TimeSheet Management Application and we need to display total working hours with minutes and second of employee. (i.e 04:30:00 according to data i share)

what i have tried?

SELECT HOUR(TIMEDIFF(end,start)) AS 'totalHour' but works only for each row not on all records.

I have also tried TIMESTAMPDIFF.

Is this possible?

EDIT

From the answer i have received from people i have tried every single of them but everytime i just get 4 or 4.5000 but it should return 06:30:00.

Answer

Try this query

SELECT
 id, 
 title, 
 TIME_FORMAT(SEC_TO_TIME(sum(TIME_TO_SEC(TIMEDIFF( end, start)))), "%h:%i") AS diff
FROM 
 tbl1
GROUP BY  
 title

According to the data that you have given answer should be 4:30. Pl cross check in you records.

FIDDLE