Resources on modeling ordered hierachies?

There a tons of articles about how to model hierarchies in SQL but I
haven't seen any about dealing with hierarchies where the order of
children is important.

The canonical example is a simple outline

1.
1.1
1.1.1
1.2
2.
2.1

etc

If I am doing an insert where parent is 1.1 it should name it 1.1.2
which to me means doing something like select max(id) + 1 where parent
= 1.1 or something like that which might turn out to be expensive.

Similarly if I want to insert something between 1.1 and 1.2 I need to
do something like update id set id = id+1 where parent = 1 and id >1

Items could of course be "promoted" this way or moved up and down the
hierarchy to be below or above their peers.

Does anybody know of a more elegant way to do this?