テーブル設計 users テーブル Column Type Options id SERIAL NOT NULL name VARCHAR(128) NOT NULL email VARCHAR(128) NOT NULL UNIQUE password VARCHAR(512) NOT NULL Option PRIMARY KEY (id) rooms テーブル Column Type Options id SERIAL NOT NULL name VARCHAR(128) NOT NULL Option PRIMARY KEY (id) room_users テーブル Column Type Options id SERIAL NOT NULL user_id INT NOT NULL room_id INT NOT NULL Option PRIMARY KEY (id) FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE FOREIGN KEY (room_id) REFERENCES rooms(id) ON DELETE CASCADE messages テーブル Column Type Options id SERIAL NOT NULL content VARCHAR(512) user_id INT NOT NULL room_id INT NOT NULL image VARCHAR(512) created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP Option PRIMARY KEY (id) FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE FOREIGN KEY (room_id) REFERENCES rooms(id) ON DELETE CASCADE