Only show hours in MYSQL DATEDIFF

I've been busy with this for hours, but I cant get it to work.

SQL

SELECT DATEDIFF(end_time, start_time) as `difference` FROM timeattendance WHERE timeattendance_id = '1484'

start_time =   2012-01-01   12:00:00
end_time =     2012-01-02   13:00:00

The difference is 25 (hours). But the output I get is 1 (day).

How can I get the 25 hours as output?

What about using TIMESTAMPDIFF?

SELECT TIMESTAMPDIFF(HOUR, start_time, end_time) 
           as `difference` FROM timeattendance WHERE timeattendance_id = '1484'

You better use TIMEDIFF instead of DATEDIFF since DATEDIFF casts all times to dates before comparing. After performing TIMEDIFF you can obtain hours with HOUR function.

SELECT HOUR(TIMEDIFF(end_time, start_time)) as `difference`;

As stated in MySQL reference, DATEDIFF only takes days in account.

If both dates are after 1970, you can substract timestamps:

SELECT ( UNIX_TIMESTAMP("2012-01-02 13:00:00") - 
         UNIX_TIMESTAMP("2012-01-01 12:00:00") ) / 3600 ...

or:

SELECT TIMEDIFF ( "2012-01-02 13:00:00", "2012-01-01 12:00:00") / 3600 ... 

You can use the TIMEDIFF and HOUR function to just extract the hour.

SELECT HOUR(TIMEDIFF(end_time, start_time)) as `difference` FROM timeattendance WHERE timeattendance_id = '1484'

http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_timediff
http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_hour