Reordering of column data in mysql

Question

I have a table like so:

categoryID      categoryName
----------------------------
     1            A
     2            B
     3            C

Answer 1

The idea with Float sounds reasanoble, just don't show these numbers to a user -)

Whenever user moves an entry up or down, you can figure out entries above and below. Just take their Order number and find mean value - that is a new order for the entry that has been moved.