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


Apache DerbyBigQueryDb2 (LUW)H2MariaDBMySQLOracle DBPostgreSQLSQL ServerSQLite20052007200920112013201520172019202110.15.2.011.5.62.0.20210.28.0.1121c8.420193.8.3

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. Union [distinct] belongs to mandatory feature E071-01.

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