Нещо подобно:
with recursive graph_cte (node1, node2, start_id)
as
(
select node1, node2, id as start_id
from graphs
where node1 = 1 -- alternatively elect the starting element using where id = xyz
union all
select nxt.node1, nxt.node2, prv.start_id
from graphs nxt
join graph_cte prv on nxt.node1 = prv.node2
)
select start_id, node1, node2
from graph_cte
order by start_id;
(изисква PostgreSQL 8.4 или по-нова версия)
