Updating MySql Column based on another Column

Hey guys I am still pretty new to MySQL and I just ran into a problem that I can't seem to figure out.

Say I have a table called "tracks" with the following columns and sample data

track_hash | track_order 
abc        | 1
abc        | 2
abc        | 3
abc        | 4
def        | 1
def        | 2
ghi        | 1

So the point is that when I display the tracks, the tracks should be ordered by the track order. So if i want to display all tracks from abc, it will display it based on the track order (1, 2, 3). Track hash "def" has two tracks...etc.

So currently in my DB I just have an empty track_order column. How would I go about to filling the track_order column with the correct data?