Recursive Insert using connect by clause - sql

Question

I have hierarchical data (right) in table in following manner which creates Hierarchy as shown in left. Tables are kept in oracle 11g.
TREE Hierarchy Tree Table
-------------- Element Parent
------ ------
P0 P0
P1 P1 P0
P11 P2 P0
C111 P11 P1
C112 P12 P1
P12 P21 P2
C121 P22 P2
C122 C111 P11
P2 C112 P11
P21 C121 P12
C211 C122 P12
C212 C211 P21
P22 C212 P21
C221 C221 P22
C222 C222 P22
My data table has values as follows. It contains values for all leaf nodes.
Data Table
Element Value
C111 3
C112 3
C121 3
C122 3
C211 3
C212 3
C221 3
C222 3
P11 6
I need to generate insert statement, preferably single insert statement which will insert rows in data table based on sum of values of the children.
Please note we need to calculate sum for only those parents whose value is not present in data table.
Data Table (Expected After Insert)
Element Value
C111 3
C112 3
C121 3
C122 3
C211 3
C212 3
C221 3
C222 3
P11 6
-- Rows to insert
P12 6
P21 6
P22 6
P1 12
P2 12
P0 24

Answer 1

If all leaf nodes are at the same height (here lvl=4), you can write a simple CONNECT BY query with a 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
The insert would look like:
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)));
If the height of the leaf nodes is unknown/unbounded this gets more hairy. The above approach wouldn't work since ROLLUP needs to know exactly how many columns are to be considered.
In that case, you could use the tree structure in a self-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

Answer 2

Here is another option using the SQL MODEL clause. I've taken some hints from what Vincent has done in his answer (use of regexp_subsr) to simplify my code.
The first part, within the WITH clause just rejigs the data and extracts out the hierarchy at each level.
The model clause, at the end of the query, brings the data up from the lowest levels. This will need additional columns added if there are more than four levels but should work no matter at what level the values are held.
I'm not entirely sure that this will work in all circumstances since I'm not that experienced with the MODEL clause but it does at least seem to work in this case.
with my_hierarchy_data as (
select
element,
value,
path,
parent,
lvl0,
regexp_substr(path, '[^/]+', 1, 2) as lvl1,
regexp_substr(path, '[^/]+', 1, 3) as lvl2,
regexp_substr(path, '[^/]+', 1, 4) as lvl3
from (
select
element,
value,
parent,
sys_connect_by_path(element, '/') as path,
connect_by_root element as lvl0
from
tree
left outer join data using (element)
start with parent is null
connect by prior element = parent
order siblings by element
)
)
select
element,
value,
path,
parent,
new_value,
lvl0,
lvl1,
lvl2,
lvl3
from my_hierarchy_data
model
return all rows
partition by (lvl0)
dimension by (lvl1, lvl2, lvl3)
measures(element, parent, value, value as new_value, path)
rules sequential order (
new_value[lvl1, lvl2, null] = sum(value)[cv(lvl1), cv(lvl2), lvl3 is not null],
new_value[lvl1, null, null] = sum(new_value)[cv(lvl1), lvl2 is not null, null],
new_value[null, null, null] = sum(new_value)[lvl1 is not null, null, null]
)
The insert statement you can use is
INSERT INTO data (elelment, value)
select element, newvalue
from <the_query>
where value is null;