   isbn_10       		VARCHAR(20)     NOT NULL,
   CONSTRAINT author_book_pk
     PRIMARY KEY (author_id, isbn_10)
-);+);

CREATE TABLE author
(
  author_id				INT         	NOT NULL	AUTO_INCREMENT,
  author_first_name		VARCHAR(50)     NOT NULL,
  author_last_name		VARCHAR(50)		NOT NULL,
  CONSTRAINT author_id_pk
    PRIMARY KEY (author_id)
);

    PRIMARY KEY (isbn_10)
);

CREATE TABLE user_owns_book
(
  user_id			INT         	NOT NULL,
  isbn_10       	VARCHAR(20)     NOT NULL,
  entry_date        DATE        	NOT NULL,
  delete_date		DATE,
  CONSTRAINT user_book_pk
    PRIMARY KEY (user_id, isbn_10)
);

CREATE TABLE user_requests_book
(
  user_id			INT         	      NOT NULL,
  isbn_10       	VARCHAR(20)     NOT NULL,
  entry_date        DATE        	NOT NULL,
  delete_date		DATE,
