Re: WITH RECURSION output ordering with trees

In article <E6A0649F1FBFA3408A37F505400E7AC215CE69(at)email(dot)attiksystem(dot)ch>,
"Philippe Lang" <philippe(dot)lang(at)attiksystem(dot)ch> writes:

> Thanks for your answer. Si there a built-in function that would allow
> generating the sort path based on the value of the lookup column,
> instead of the id, which has no meaning at all?

> If yes, we would get instead:

> depth | id | lookup | parent_id
> -------+-----+--------+-----------
> 0 | 1 | a1 |
> 1 | 2 | b11 | 1
> 2 | 645 | c111 | 2
> 2 | 823 | c112 | 2
> 2 | 243 | c113 | 2
> 1 | 6 | b12 | 1
> 2 | 845 | c121 | 6
> 2 | 583 | c122 | 6
> 1 | 9 | b13 | 1
> 2 | 10 | c131 | 9

Try this:

WITH RECURSIVE parse_tree (depth, id, lookup, parent_id, path) AS (
SELECT 0, parent.id, parent.lookup, parent.parent_id, parent.lookup::text
FROM recursion AS parent
WHERE parent_id IS NULL
UNION ALL
SELECT parent.depth + 1, child.id, child.lookup, child.parent_id,
parent.path || '.' || child.lookup
FROM parse_tree parent
JOIN recursion AS child ON child.parent_id = parent.id
)
SELECT depth, id, lookup, parent_id
FROM parse_tree
ORDER BY path