Recursive query - Oracle - sql

Question

I have this data and expected result:
Data Expected Result
No A B A B
1 10 500 10 500
2 10 c=20 20 400
3 20 400 30 600
4 30 600 30 700
5 30 c=40 30 800
6 30 c=50 40 700
7 40 700 50 900
8 50 c=60 60 900
9 60 c=70 70 900
10 70 900 10 400
I need to perform a self join and get the result.
For line number 1 the expected result is same as the row.
For line number 2, I need to take the substring of column B (c=20) as 20 and join with column B and get the result as 400.
Lines number 5 and 6 need to substring column B and get the result from column A.
I tried a recursive query, but still am not getting the expected result.
with rec(A, B, nested) as
(
select A, B, case when instr(B, 'C=') != 0 then substr(B, instr(B, 'C=')) as nested
from table
union all
select A, rec.B from table
inner join rec
on (table.A = rec.nested)
)
select A, B, nested from rec;

Answer 1

Answer for the initial version of the question
You do not need a recursive query. To get your desired output you just need to exclude the rows where B starts with c=:
SELECT a, b
FROM table_name
WHERE b NOT LIKE 'c=%';
Which, for the sample data:
CREATE TABLE table_name (no, a, b) AS
SELECT 1, 10, '500' FROM DUAL UNION ALL
SELECT 2, 10, 'c=20' FROM DUAL UNION ALL
SELECT 3, 20, '400' FROM DUAL UNION ALL
SELECT 4, 30, '600' FROM DUAL UNION ALL
SELECT 5, 30, 'c=40' FROM DUAL UNION ALL
SELECT 6, 30, 'c=50' FROM DUAL UNION ALL
SELECT 7, 40, '700' FROM DUAL UNION ALL
SELECT 8, 50, '800' FROM DUAL;
Outputs your desired output:
A
B
10
500
20
400
30
600
40
700
50
800
fiddle
Answer for the 3rd edit of the question
You can use a hierarchical query:
SELECT DISTINCT
CONNECT_BY_ROOT a AS a,
b
FROM table_name
WHERE CONNECT_BY_ISLEAF = 1
CONNECT BY
PRIOR b LIKE 'c=%'
AND PRIOR SUBSTR(b, 3) = a
ORDER BY a, b;
Which, for the sample data:
CREATE TABLE table_name (no, a, b) AS
SELECT 1, 10, '500' FROM DUAL UNION ALL
SELECT 2, 10, 'c=20' FROM DUAL UNION ALL
SELECT 3, 20, '400' FROM DUAL UNION ALL
SELECT 4, 30, '600' FROM DUAL UNION ALL
SELECT 5, 30, 'c=40' FROM DUAL UNION ALL
SELECT 6, 30, 'c=50' FROM DUAL UNION ALL
SELECT 7, 40, '700' FROM DUAL UNION ALL
SELECT 8, 50, 'c=60' FROM DUAL UNION ALL
SELECT 9, 60, 'c=70' FROM DUAL UNION ALL
SELECT 10, 70, '900' FROM DUAL;
Outputs:
A
B
10
400
10
500
20
400
30
600
30
700
30
900
40
700
50
900
60
900
70
900
fiddle