NOTE : Since order is a reserved keyword you can use any other
name for the column
This can be achieved by taking order column in your table.
For Eg:
id taskname order
1 firsttask 1
2 firsttask 2
3 firsttask 4
4 firsttask 3
5 firsttask 5
Then while fetching get it order by asc for order column
SELECT * FROM tasks ORDER BY order ASC
Now you may allow the user to add the order in which the items look like by text box or dragable of jquery and then while storing in the database table you can store it via that order
solved Listing data from database in hierachy and returning it in that order to the database