Recursion in SQL-3

Limited forms of recursion are considered important.

Linear recursion: only 1 occurrence of a recursive predicate

in the body

Path( X, Y ) :- Edge( X, Y )

Path( X, Y ) :- Edge( X, Z ), Path( Z, Y ).

WITH

Pairs AS SELECT origin, dest FROM EDGE

RECURSIVE Path(origin, dest) AS

Pairs

UNION

(SELECT Pairs.origin, Path.to

FROM Pairs, Path

WHERE Pairs.to = Path.origin)

SELECT * FROM Path;