   title         	VARCHAR(100)	NOT NULL,
   author        VARCHAR(255) NOT NULL,
   publishers		VARCHAR(100)	NOT NULL,
-  publish_date		DATE			NOT NULL,
+  publish_date		YEAR			NOT NULL,
   thumbnail_url		VARCHAR(255),			
   CONSTRAINT isbn_pk 
     PRIMARY KEY (isbn)

(
  user_id			INT         	      NOT NULL,
  isbn       	VARCHAR(13)     NOT NULL,
  entry_date        DATE        	NOT NULL,
  delete_date		DATE,
  CONSTRAINT user_book_pk
    PRIMARY KEY (user_id, isbn)
);

(
  user_id			INT         	NOT NULL,
  isbn       	VARCHAR(13)     NOT NULL,
  CONSTRAINT user_book_pk
    PRIMARY KEY (user_id, isbn)
);
