Welcome to Software Development on Codidact!

Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.

Review Suggested Edit

You can't approve or reject suggested edits because you haven't yet earned the Edit Posts ability.

How to break infinite loop in CTE

I have a parent child relation in my table, with possibly circular cases. Is it possible to break the infinite recursivity in CTE checking values of all previous rows? I would need something like this:
with my_cte(childId, parentId, col1)
AS (
SELECT r.childId, r.parentId, r.col1
FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
UNION ALL
SELECT rel.childId, rel.parentId, rel.col1
FROM My_Table rel INNER JOIN my_cte sd ON rel.childId = sd.parentId where (rel.col1 = 1 OR rel.col1 = 2) AND ...
-- check that rel.childId, rel.parentId not in previous rows
)
SELECT DISTINCT * from shared_documents
How can I achieve this? Or how to approach this?
Example table with records would be:
~~childId | parentId | col1~~
~~1 | 3 | 1~~
~~1 | 4 | 1~~
~~3 | 5 | 1~~
~~5 | 1 | 1 -- circular case~~
~~6 | 2 | 1~~
~~5 | 7 | 1~~
~~If I ask for hierarcy related to 1, I should get~~
~~childId | parentId | col1~~
~~1 | 3 | 1~~
~~1 | 4 | 1~~
~~3 | 5 | 1~~
~~5 | 1 | 1 -- circular case~~
~~5 | 7 | 1~~
- 1 has two parents: 3 and 4.
- 3 has 1 parent: 5
- 5 has 2 parents: 1 and 7. But 1 brings the infinite loop, so the query should ignore this. And continue to the next row.

I have a parent-child relation in my table, with possibly circular cases. Is it possible to break the infinite recursion in CTE checking values of all previous rows? I would need something like this:
with my_cte(childId, parentId, col1)
AS (
SELECT r.childId, r.parentId, r.col1
FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
UNION ALL
SELECT rel.childId, rel.parentId, rel.col1
FROM My_Table rel INNER JOIN my_cte sd ON rel.childId = sd.parentId where (rel.col1 = 1 OR rel.col1 = 2) AND ...
-- check that rel.childId, rel.parentId not in previous rows
)
SELECT DISTINCT * from shared_documents
How can I achieve this? Or how to approach this?
Example table with records would be:
| childId | parentId | col1 |
|---------|----------|------|
| 1 | 3 | 1
| 1 | 4 | 1
| 3 | 5 | 1
| 5 | 1 | 1 -- circular case
| 6 | 2 | 1
| 5 | 7 | 1
If I ask for hierarchy related to 1, I should get
| childId | parentId | col1 |
|---------|----------|------|
| 1 | 3 | 1
| 1 | 4 | 1
| 3 | 5 | 1
| 5 | 1 | 1 -- circular case
| 5 | 7 | 1
- 1 has two parents: 3 and 4.
- 3 has 1 parent: 5
- 5 has 2 parents: 1 and 7. But 1 brings the infinite loop, so the query should ignore this. And continue to the next row.

sql sql-server common-table-expression

Communities

Review Suggested Edit