On 20/12/2017 22:31, Shane Dev wrote:
Hello,
I have an edges table -
sqlite> .sch edges
CREATE TABLE edges(parent, child);
sqlite> select * from edges;
parent child
1 2
1 3
2 4
3 1
4 5
5 2
Here we have two cycles -
1) 1 => 3 => 1 (length 1)
2) 2 => 4 => 5 => 2 (length 3)
Cycles cause recursive common table expression queries to become infinite
loops.
Maybe you could show an example of such queries? This:
with recursive Visit(node) as (
select parent from Edges where parent = 1
union
select child from Edges join Visit on parent = node
)
select node from Visit;
returns a finite result (note that use of 'union' rather than 'union
all').
Life.
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