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Q&A 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 recursion in CTE checking values of all previous rows? I would need something like thi...

3 answers  ·  posted 3y ago by artaxerxe‭  ·  edited 15d ago by Michael‭

Question sql sql-server common-table-expression
#7: Post edited by user avatar Michael‭ · 2024-04-05T10:25:04Z (15 days ago)
Fix table markdown 
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
sql sql-server common-table-expression
#6: Post edited by user avatar Alexei‭ · 2024-04-04T07:46:28Z (16 days ago)
added the actual CTE tag
#5: Nominated for promotion by user avatar Alexei‭ · 2021-04-21T09:17:34Z (almost 3 years ago)
#4: Post edited by user avatar artaxerxe‭ · 2021-04-19T13:16:37Z (about 3 years ago)
  • 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(id, childId, parentId, col1, col2)
  • AS (
  • SELECT r.id, r.childId, r.parentId, r.col1, r.col2
  • FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
  • UNION ALL
  • SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
  • 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:
  • id | childId | parentId | col1 | col2
  • 1 | 1 | 3 | 1 | null
  • 2 | 1 | 4 | 1 | null
  • 3 | 3 | 5 | 1 | null
  • 4 | 5 | 1 | 1 | null -- circular case
  • 5 | 6 | 2 | 1 | null
  • 6 | 5 | 7 | 1 | null
  • If I ask for hierarcy related to 1, I should get
  • id | childId | parentId | col1 | col2
  • 1 | 1 | 3 | 1 | null
  • 2 | 1 | 4 | 1 | null
  • 3 | 3 | 5 | 1 | null
  • 4 | 5 | 1 | 1 | null -- circular case
  • 6 | 5 | 7 | 1 | null
  • - 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 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.
#3: Post edited by user avatar artaxerxe‭ · 2021-04-19T13:03:53Z (about 3 years ago)
  • 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(id, childId, parentId, col1, col2)
  • AS (
  • SELECT r.id, r.childId, r.parentId, r.col1, r.col2
  • FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
  • UNION ALL
  • SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
  • 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?
  • 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(id, childId, parentId, col1, col2)
  • AS (
  • SELECT r.id, r.childId, r.parentId, r.col1, r.col2
  • FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
  • UNION ALL
  • SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
  • 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:
  • id | childId | parentId | col1 | col2
  • 1 | 1 | 3 | 1 | null
  • 2 | 1 | 4 | 1 | null
  • 3 | 3 | 5 | 1 | null
  • 4 | 5 | 1 | 1 | null -- circular case
  • 5 | 6 | 2 | 1 | null
  • 6 | 5 | 7 | 1 | null
  • If I ask for hierarcy related to 1, I should get
  • id | childId | parentId | col1 | col2
  • 1 | 1 | 3 | 1 | null
  • 2 | 1 | 4 | 1 | null
  • 3 | 3 | 5 | 1 | null
  • 4 | 5 | 1 | 1 | null -- circular case
  • 6 | 5 | 7 | 1 | null
  • - 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.
#2: Post edited by user avatar artaxerxe‭ · 2021-04-19T12:53:39Z (about 3 years ago)
  • 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(id, childId, parentId, col1, col2)
  • AS (
  • SELECT r.id, r.childId, r.parentId, r.col1, r.col2
  • FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
  • UNION ALL
  • SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
  • 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 not in previous rel.childId
  • )
  • SELECT DISTINCT * from shared_documents
  • How can I achieve this? Or how to approach this?
  • 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(id, childId, parentId, col1, col2)
  • AS (
  • SELECT r.id, r.childId, r.parentId, r.col1, r.col2
  • FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
  • UNION ALL
  • SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
  • 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?
#1: Initial revision by user avatar artaxerxe‭ · 2021-04-19T12:40:13Z (about 3 years ago) 
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(id, childId, parentId, col1, col2)
    AS (
    SELECT r.id, r.childId, r.parentId, r.col1, r.col2
	FROM My_Table r WHERE r.childId = 'x' AND (r.col1 = 1 or r.col1 = 2)
	UNION ALL 
	SELECT rel.id, rel.childId, rel.parentId, rel.col1, rel.col2
		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 not in previous rel.childId
    )
    SELECT DISTINCT * from shared_documents

How can I achieve this? Or how to approach this?
sql sql-server common-table-expression