Modelling hierarchy in the relational database

I am constructing a database to model hierarchy, e.g.  A
|

 B
|

 C

I envisage a table parent consisiting fields parent, child and would store records A,B and B,C. Would I also need to store record A,C?

I.e. can SQL act recursively to determina all the children of a given node (could it retrieve B and C if I queried for the children of A with only records A,B and B,C stored?)

Many thanks in advance for any help on this Received on Fri Aug 17 2001 - 16:08:17 CDT