Question

Just wanted to know what would happen if in my book database i had two different authors which have the same name. How could i redesign my database to sort this problem out? Do i have to assign primary and secondary keys or something? By the way this question is related to my previous one.

Answer 1

An AUTHORS table would help your book database – you could store the author info once, but associate it with multiple books:

DROP TABLE IF EXISTS `example`.`authors`;
CREATE TABLE  `example`.`authors` (
  `author_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `firstname` varchar(45) NOT NULL,
  `lastname` varchar(45) NOT NULL,
   PRIMARY KEY (`author_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Books can have multiple authors, so you’d need a many-to-many table to relate authors to books:

DROP TABLE IF EXISTS `example`.`book_authors_map`;
CREATE TABLE  `example`.`book_authors_map` (
  `book_id` int(10) unsigned NOT NULL,
  `author_id` int(10) unsigned NOT NULL,
  PRIMARY KEY (`book_id`,`author_id`),
  KEY `FK_authors` (`author_id`),
  CONSTRAINT `FK_books` FOREIGN KEY (`book_id`) REFERENCES `books` (`book_id`),
  CONSTRAINT `FK_authors` FOREIGN KEY (`author_id`) REFERENCES `authors` (`author_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;