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


Apache DerbyBigQueryDb2 (LUW)H2MariaDBMySQLOracle DBPostgreSQLSQL ServerSQLite2009201120132015201720192021✓ 3.8.3+⊘ 3.5.7 - 3.7.11⊘ 2008R2 - 2022✓ 8.4+⊘ 8.3⊘ 11gR1 - 21c✓ 8.0.11+⊘ 5.0 - 5.7✓ 10.2+⊘ 5.1 - 10.1⊘ 2.0.204 - 2.1.214⊘ 1.4.191 - 1.4.200⊘ 9.7 - 11.5.8⊘ 2.0⊘ 10.15.1.3 - 10.16.1.1

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

WITH RECURSIVE path (a, b) AS (
  SELECT edges.* FROM edges
                WHERE a = 1
UNION
  SELECT edges.* FROM edges
                 JOIN path 
                   ON edges.a = path.b
)
SELECT *
  FROM path

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, “Recursive query”. Union [distinct] belongs to mandatory feature E071-01.

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