Re: tree-structured query

On fös, 2006-09-29 at 15:00 -0700, chester c young wrote:
> in a simple tree structured table
>
> table t(
> id primary key,
> pnt_id references t( id ),
> name
> );
>
> does anyone know an easy howbeit sneaky way of determining ancestory
> and decendency without recursive functions,

how about
CREATE TABLE ancestry (
ans_id int, desc_id int
)

for each record of t ,
for each ancestor of id,
insert a record (ans_id,id) into anscestry

this can be maintained by application, or by triggers.

to get all ancestors of a particular id X:
SELECT name from t JOIN ancestry ON (id=ans_id)
WHERE desc_id=X;

to get descendents:
SELECT name from t JOIN ancestry ON (id=desc_id)
WHERE ans_id=X;

indexes on ancestry(ans_id) and ancestry(desc_id)
might be called for.

hope this helps
gnari