I'm looking at a query generated by SQLAlchemy. It works; Postgres is perfectly happy to run it, and it gives answers that make sense to the guy who wrote it. But I don't understand why it works.
Stripped way down ... CREATE VIEW relation_a (id_c, id_v) AS VALUES (1, 20), (2, 21), (3, 22); CREATE VIEW relation_b (id_c, id_v, id_p) AS VALUES (1, 20, 300), (2, 21, 301); CREATE VIEW relation_c (id_p) AS VALUES (301); SELECT * FROM relation_a LEFT JOIN relation_b JOIN relation_c ON (relation_c.id_p = relation_b.id_p) ON (relation_a.id_c = relation_b.id_c AND relation_a.id_v = relation_b.id_v); I would have claimed before seeing this example that it wasn't even grammatical; I thought the only legal place to write the ON clause was immediately after the JOIN. Apparently not. How should I read this query? I'd appreciate any help understanding this. -- Mark Jeffcoat Austin, TX
