问题
Given a simple (id, description) table t1, such as
id description
-- -----------
1 Alice
2 Bob
3 Carol
4 David
5 Erica
6 Fred
And a parent-child relationship table t2, such as
parent child
------ -----
1 2
1 3
4 5
5 6
Oracle offers a way of traversing this as a tree with some custom syntax extensions:
select parent, child, sys_connect_by_path(child, '/') as "path"
from t2
connect by prior parent = child
The exact syntax is not important, and I've probably made a mistake in the above. The important thing is that the above will produce something that looks like
parent child path
------ ----- ----
1 2 /1/2
1 3 /1/3
4 5 /4/5
4 6 /4/5/6
5 6 /5/6
My question is this: is it possible to join another table within the sys_connect_by_path(), such as the t1 table above, to produce something like:
parent child path
------ ----- ----
1 2 /Alice/Bob
1 3 /Alice/Carol
... and so on...
回答1:
In your query, replace T2 with a subquery that joins T1 and T2, and returns parent, child and child description. Then in the sys_connect_by_path function, reference the child description from your subquery.
回答2:
Based on Mike McAllister's idea, the following uses a derived table to achieve the desired result:
select
T.PARENT
,T.CHILD
,sys_connect_by_path(T.CDESC, '/')
from
(
select
t2.parent as PARENT
,t2.child as CHILD
,t1.description as CDESC
from
t1, t2
where
t2.child = t1.id
) T
where
level > 1 and connect_by_isleaf = 1
connect by prior
T.CHILD = T.PARENT
In my problem, all the parents are anchored under a "super-parent" root, which means that the paths can be fully described with SYS_CONNECT_BY_PATH, thereby obviating the need for cagcowboy's technique of concatenating the parent with the path.
回答3:
SELECT parent, child, parents.description||sys_connect_by_path(childs.description, '/') AS "path"
FROM T1 parents, T1 childs, T2
WHERE T2.parent = parents.id
AND T2.child = childs.id
CONNECT BY PRIOR parent = child
来源：https://stackoverflow.com/questions/117512/joining-other-tables-in-oracle-tree-queries