Create MySQL trigger that updates position of each row when sorted by a specific field
You (as in, the user) won't generally sort data within a table.  You (as in, a user) will sort the output from queries.

The order that the data is stored is generally irrelevant to you, and the database will store the data in a way that makes sense for it.

If you want/need the data ordered when you run a query, put the order by statement in the query...

select x,y,z 
from table1
order by x asc, y desc