CREATE TABLE collection ( id SERIAL PRIMARY KEY, card_id TEXT NOT NULL, quality TEXT NOT NULL CHECK (quality IN ('online', 'near mint', 'lightly played', 'moderately played', 'heavily played', 'damaged')), quantity INT NOT NULL CHECK (quantity >= 0), UNIQUE (card_id, quality) ); ALTER TABLE ONLY collection ADD CONSTRAINT collection_card_id_fkey FOREIGN KEY (card_id) REFERENCES cards (id) ON DELETE CASCADE; CREATE INDEX collection_card_id_idx ON collection (card_id);