Can I use… with recursive (… union [distinct] …)

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Union [distinct] within with recursive can be used to omit duplicate rows and thus preventing infinite loops.

WITH RECURSIVE path (from, to) AS (
   SELECT from, to
     FROM edges
    WHERE id = ?
   SELECT from, to
     FROM path
     JOIN edges ON edges.from =
) …

The example properly terminates even if the graph stored in the edges table has cycles.

Normative References

The with recursive clause is defined in ISO/IEC 9075:2016-2 as part of optional feature T131. Union [distinct] belongs to mandatory feature E071-01.

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