Oracle - Parent - child + fill mising hierarchy levels - oracle

Question

I have created my fiddle example here: FIDDLE
Here is also athe code from the fiddle:
CREATE TABLE T1(ID INT, CODE INT, CODE_NAME VARCHAR(100), PARENT_ID INT);
INSERT INTO T1 VALUES(100,1,'LEVEL 1', NULL);
INSERT INTO T1 VALUES(110,11,'LEVEL 2', 100);
INSERT INTO T1 VALUES(120,111,'LEVEL 3', 110);
INSERT INTO T1 VALUES(125,112,'LEVEL 3', 110);
INSERT INTO T1 VALUES(130,1111,'LEVEL 4', 120);
INSERT INTO T1 VALUES(200,2,'LEVEL 1', NULL);
INSERT INTO T1 VALUES(210,21,'LEVEL 2', 200);
INSERT INTO T1 VALUES(300,3,'LEVEL 1', NULL);
I have trouble finding the soultuin how to get from that table this result:
| CODE | CODE NAME | CODE 1 |CODE NAME 1| CODE 2 | CODE NAME 2| CODE 3 | CODE NAME 3 |
+--------+------------+--------+-----------+--------+------------+--------+-------------+
| 1 | LEVEL 1 | 11 | LEVEL 2 | 111 | LEVEL 3 | 1111 | LEVEL 4 |
| 1 | LEVEL 1 | 11 | LEVEL 2 | 112 | LEVEL 3 | 112 | LEVEL 3 |
| 2 | LEVEL 1 | 21 | LEVEL 2 | 21 | LEVEL 2 | 21 | LEVEL 2 |
| 3 | LEVEL 1 | 3 | LEVEL 1 | 3 | LEVEL 1 | 3 | LEVEL 1 |
I have tried something with connect by but that is not what I need(I think)...
The max I will ever have is 4 levels and if there are only two levels in the data then the 3rd and the 4th level should be filled wiht the values of the last existing value. The same rule is valid if there are 3 levels or 1 level.

Answer 1

You can use a recursive sub-query:
WITH hierarchy (
code, code_name,
code1, code_name1,
code2, code_name2,
code3, code_name3,
id, depth
) AS (
SELECT code,
code_name,
CAST(NULL AS INT),
CAST(NULL AS VARCHAR2(100)),
CAST(NULL AS INT),
CAST(NULL AS VARCHAR2(100)),
CAST(NULL AS INT),
CAST(NULL AS VARCHAR2(100)),
id,
1
FROM t1
WHERE parent_id IS NULL
UNION ALL
SELECT h.code,
h.code_name,
CASE depth WHEN 1 THEN COALESCE(t1.code, h.code) ELSE h.code1 END,
CASE depth WHEN 1 THEN COALESCE(t1.code_name, h.code_name) ELSE h.code_name1 END,
CASE depth WHEN 2 THEN COALESCE(t1.code, h.code1) ELSE h.code2 END,
CASE depth WHEN 2 THEN COALESCE(t1.code_name, h.code_name1) ELSE h.code_name2 END,
CASE depth WHEN 3 THEN COALESCE(t1.code, h.code2) ELSE h.code3 END,
CASE depth WHEN 3 THEN COALESCE(t1.code_name, h.code_name2) ELSE h.code_name3 END,
t1.id,
h.depth + 1
FROM hierarchy h
LEFT OUTER JOIN t1
ON (h.id = t1.parent_id)
WHERE depth < 4
)
CYCLE code, depth SET is_cycle TO 1 DEFAULT 0
SELECT code, code_name,
code1, code_name1,
code2, code_name2,
code3, code_name3
FROM hierarchy
WHERE depth = 4;
Which, for the sample data:
CREATE TABLE T1(ID, CODE, CODE_NAME, PARENT_ID) AS
SELECT 100, 1, 'LEVEL 1', NULL FROM DUAL UNION ALL
SELECT 110, 11, 'LEVEL 2', 100 FROM DUAL UNION ALL
SELECT 120, 111, 'LEVEL 3', 110 FROM DUAL UNION ALL
SELECT 130, 1111, 'LEVEL 4', 120 FROM DUAL UNION ALL
SELECT 200, 2, 'LEVEL 1', NULL FROM DUAL UNION ALL
SELECT 210, 21, 'LEVEL 2a', 200 FROM DUAL UNION ALL
SELECT 220, 22, 'LEVEL 2b', 200 FROM DUAL UNION ALL
SELECT 230, 221, 'LEVEL 3', 220 FROM DUAL UNION ALL
SELECT 300, 3, 'LEVEL 1', NULL FROM DUAL;
Outputs:
CODE
CODE_NAME
CODE1
CODE_NAME1
CODE2
CODE_NAME2
CODE3
CODE_NAME3
1
LEVEL 1
11
LEVEL 2
111
LEVEL 3
1111
LEVEL 4
3
LEVEL 1
3
LEVEL 1
3
LEVEL 1
3
LEVEL 1
2
LEVEL 1
21
LEVEL 2a
21
LEVEL 2a
21
LEVEL 2a
2
LEVEL 1
22
LEVEL 2b
221
LEVEL 3
221
LEVEL 3
db<>fiddle here

Answer 2

For sample data you posted:
SQL> select * from t1;
ID CODE CODE_NAME PARENT_ID
---------- ---------- ---------- ----------
100 1 LEVEL 1
110 11 LEVEL 2 100
120 111 LEVEL 3 110
130 1111 LEVEL 4 120
200 2 LEVEL 1
210 21 LEVEL 2 200
6 rows selected.
SQL>
an ugly (and who-knows-how-performant) query that, though, returns desired result is
with temp as
(select id, code, code_name, parent_id, level lvl,
row_number() over (partition by level order by id) rn
from t1
start with parent_id is null
connect by prior id = parent_id
),
a as
(select * from temp where lvl = 1),
b as
(select * from temp where lvl = 2),
c as
(select * from temp where lvl = 3),
d as
(select * from temp where lvl = 4)
select
a.code code1, a.code_name code_name1,
coalesce(b.code, a.code) code2, coalesce(b.code_name, a.code_name) code_name2,
coalesce(c.code, b.code, a.code) code3, coalesce(c.code_name, b.code_name, a.code_name) code_name3,
coalesce(d.code, c.code, b.code, a.code) code4, coalesce(d.code_name, c.code_name, b.code_name, a.code_name) code_name4
from a join b on b.rn = a.rn
left join c on c.rn = b.rn
left join d on d.rn = c.rn;
which results in
CODE1 CODE_NAME1 CODE2 CODE_NAME2 CODE3 CODE_NAME3 CODE4 CODE_NAME4
---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
1 LEVEL 1 11 LEVEL 2 111 LEVEL 3 1111 LEVEL 4
2 LEVEL 1 21 LEVEL 2 21 LEVEL 2 21 LEVEL 2
What does it do?
temp CTE creates a hierarchy; additionally, row_number function numbers each row within the same level
a, b, c, d CTEs extract values belonging to their own level value (you said there can be up to 4 levels)
finally, coalesce on column names along with outer join do the job

Answer 3

From your example I assume you want to see one row per root key as your example is not realy a tree but a bamboo
If so this is a trivial PIVOT query - unfortunately limited to some level deep (here example for your 4 levels)
with p (ROOT_CODE, CODE, CODE_NAME, ID, PARENT_ID, LVL) as (
select CODE, CODE, CODE_NAME, ID, PARENT_ID, 1 LVL from t1 where PARENT_ID is NULL
union all
select p.ROOT_CODE, c.CODE, c.CODE_NAME, c.ID, c.PARENT_ID, p.LVL+1 from t1 c
join p on c.PARENT_ID = p.ID),
t2 as (
select ROOT_CODE, CODE,CODE_NAME,LVL from p)
select * from t2
PIVOT
(max(CODE) code, max(CODE_NAME) code_name
for LVL in (1 as "LEV1",2 as "LEV2",3 as "LEV3",4 as "LEV4")
);
ROOT_CODE LEV1_CODE LEV1_CODE_ LEV2_CODE LEV2_CODE_ LEV3_CODE LEV3_CODE_ LEV4_CODE LEV4_CODE_
---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
1 1 LEVEL 1 11 LEVEL 2 111 LEVEL 3 1111 LEVEL 4
2 2 LEVEL 1 21 LEVEL 2
The recursive CTE calculates the ROOT_CODE required for the pivot.
I' leaving as an exercise to fill the not defined levels (with COALESCE) with the previous values as in your example.
In case (as commented) you nedd oner row for each leave key a simple solution based on CONNECT_BY_PATHis possible.
I'm using again *recursive CTEcalculating the path from *root* to the *current node* and finaly filtering in the result the *leaves* (IDthat are notPARENT_ID`)
with p ( CODE, CODE_NAME, ID, PARENT_ID, PATH) as (
select CODE, CODE_NAME, ID, PARENT_ID, to_char(CODE)||'|'||CODE_NAME PATH from t1 where PARENT_ID is NULL
union all
select c.CODE, c.CODE_NAME, c.ID, c.PARENT_ID, p.PATH ||'|'||to_char(c.CODE)||'|'||c.CODE_NAME from t1 c
join p on c.PARENT_ID = p.ID)
select PATH from p
where ID in (select ID from T1 MINUS select PARENT_ID from T1)
order by 1;
The result holds for any level deepness and is concatenated string with delimiter
PATH
----------------------------------------------
1|LEVEL 1|11|LEVEL 2|111|LEVEL 3|1111|LEVEL 4
1|LEVEL 1|11|LEVEL 2|112|LEVEL 3
2|LEVEL 1|21|LEVEL 2
3|LEVEL 1
Use substr instr to extract and coalesce for the default values.

Answer 4

Solution using a hierarchical query - we record the code and code_name paths, then we break them apart. Level is used to decide whether we populate data from the paths or from the leaf node. The solution assumes the codes and code names do not contain the forward-slash character (if they may, use another separator in the paths - perhaps some control character like chr(31), the unit separator character in ASCII and Unicode).
To break apart the paths, I used regexp_substr as it's easier to work with (and, moreover, I assumed all codes and code names are non-null - if they may be null, the solution can be adapted easily). If this proves to be slow, that can be changed to use standard string functions.
with
p (code, code_name, parent_id, lvl, code_pth, code_name_pth) as (
select code, code_name, parent_id, level,
sys_connect_by_path(code, '/') || ',' ,
sys_connect_by_path(code_name, '/') || ','
from t1
where connect_by_isleaf = 1
start with parent_id is null
connect by parent_id = prior id
)
select case when lvl = 1 then code
else to_number(regexp_substr(code_pth, '[^/]+', 1, 1)) end as code,
case when lvl =1 then code_name
else regexp_substr(code_name_pth, '[^/]+', 1, 1) end as code_name,
case when lvl <= 2 then code
else to_number(regexp_substr(code_pth, '[^/]+', 1, 2)) end as code_1,
case when lvl <= 2 then code_name
else regexp_substr(code_name_pth, '[^/]+', 1, 2) end as code_name_1,
case when lvl <= 3 then code
else to_number(regexp_substr(code_pth, '[^/]+', 1, 3)) end as code_2,
case when lvl <= 3 then code_name
else regexp_substr(code_name_pth, '[^/]+', 1, 3) end as code_name_2,
code as code_3,
code_name as code_name_3
from p;