Le lundi 16 septembre 2013 à 08:30 -0700, David Johnston a écrit : > Ladislav Lenart wrote > > Hello all. > > > > I am curious about the following usage of CTEs: > > > > Imagine three tables: > > * item (id, item_type1_id, item_type2_id, ...) > > * item_type1 (id, ...) > > * item_type2 (id, ...) > > where > > * item_type1_id is FK to item_type1 (id) > > * item_type2_id is FK to item_type2 (id) > > The mental model that comes to mind is: > > item (item_id) > item_type1 (type1_id, item_id <FK>) > item_type2 (type2_id, item_id <FK>) > > Or even better: > > item (item_id <PK>) > item_type1 (item_id <PK; FK>) > > item_type2 (item_id <PK; FK>) >
I would suggest : item (item_id <PK>, id_type integer) item_type1 (item_id <PK; FK>) item_type2 (item_id <PK; FK>) where item.id_type is either type_1 or type_2 So that the application knows which table to use? But chances are the OP can't change his model easily. -- Salutations, Vincent Veyron http://marica.fr/ Gestion des contentieux juridiques, des sinistres d'assurance et des contrats -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
