Re: WITH RECURSION output ordering with trees

pgsql-sql-owner(at)postgresql(dot)org wrote:
> 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

Works great, thanks! Of course, concatenating lookups...

Best regards,

Philippe