CREATE TABLE  keywords (
  kwID     INT AUTO_INCREMENT PRIMARY KEY,
  keyword  VARCHAR(64) );

CREATE TABLE  url_title (
  urlID  INT AUTO_INCREMENT PRIMARY KEY,
  url    VARCHAR(128),
  title  VARCHAR(128) );
  
CREATE TABLE  www_index (
  kwID   INT,
  urlID  INT,
  PRIMARY KEY ( kwID, urlID ),
  FOREIGN KEY ( kwID  ) REFERENCES  keywords  ( kwID ),
  FOREIGN KEY ( urlID ) REFERENCES  url_title ( urlID ) );