no one in the company i work for knows how to sove the below

we have a register of data which use a parent / child relationship. when
you extract the data it is easy to follow if you can put it back into this
parent / child relationship, however it comes out in basically a random
order. i have the following data to go off on each record,

column 1 = child number
column 2 = parent number

you will notice that each records parent number is equal to the child number
of the above record.

what i need to some how do is sort the data so the child record sits under
the parent record.

Column 1 Column 2
000042009500 000000016150
000042150650 000042009500
000043040100 000042150650
000048469200 000043040100
000048348400 000048469200

Cheers Pete