Hvis alle bladknuder er i samme højde (her lvl=4), kan du skrive en simpel CONNECT BY-forespørgsel med en ROLLUP:
SQL> SELECT lvl0,
2 regexp_substr(path, '[^/]+', 1, 2) lvl1,
3 regexp_substr(path, '[^/]+', 1, 3) lvl2,
4 SUM(VALUE) sum_value
5 FROM (SELECT sys_connect_by_path(t.element, '/') path,
6 connect_by_root(t.element) lvl0,
7 t.element, d.VALUE, LEVEL lvl
8 FROM tree t
9 LEFT JOIN DATA d ON d.element = t.element
10 START WITH t.PARENT IS NULL
11 CONNECT BY t.PARENT = PRIOR t.element)
12 WHERE VALUE IS NOT NULL
13 AND lvl = 4
14 GROUP BY lvl0, ROLLUP(regexp_substr(path, '[^/]+', 1, 2),
15 regexp_substr(path, '[^/]+', 1, 3));
LVL0 LVL1 LVL2 SUM_VALUE
---- ----- ----- ----------
P0 P1 P11 6
P0 P1 P12 6
P0 P1 12
P0 P2 P21 6
P0 P2 P22 6
P0 P2 12
P0 24
Indlægget ville se sådan ud:
INSERT INTO data (element, value)
(SELECT coalesce(lvl2, lvl1, lvl0), sum_value
FROM <query> d_out
WHERE NOT EXISTS (SELECT NULL
FROM data d_in
WHERE d_in.element = coalesce(lvl2, lvl1, lvl0)));
Hvis højden af bladknuderne er ukendt/ubegrænset, bliver dette mere behåret. Ovenstående tilgang ville ikke fungere, da ROLLUP skal vide præcis, hvor mange kolonner der skal tages i betragtning.
I så fald kan du bruge træstrukturen i en selv-join :
SQL> WITH HIERARCHY AS (
2 SELECT t.element, path, VALUE
3 FROM (SELECT sys_connect_by_path(t.element, '/') path,
4 connect_by_isleaf is_leaf, ELEMENT
5 FROM tree t
6 START WITH t.PARENT IS NULL
7 CONNECT BY t.PARENT = PRIOR t.element) t
8 LEFT JOIN DATA d ON d.element = t.element
9 AND t.is_leaf = 1
10 )
11 SELECT h.element, SUM(elements.value)
12 FROM HIERARCHY h
13 JOIN HIERARCHY elements ON elements.path LIKE h.path||'/%'
14 WHERE h.VALUE IS NULL
15 GROUP BY h.element
16 ORDER BY 1;
ELEMENT SUM(ELEMENTS.VALUE)
------- -------------------
P0 24
P1 12
P11 6
P12 6
P2 12
P21 6
P22 6