Fremmednøgle

Hej,

jeg kan ikke helt forstå hvorfor denne kode ikke virker:

CREATE TABLE `City` (
  `zipCode` INTEGER(4) NOT NULL,
  `cityName` VARCHAR(50) NOT NULL
  );
CREATE TABLE `Members` (
  `memberID` INTEGER AUTO_INCREMENT,
  `firstName` VARCHAR(30) NOT NULL,
  `lastName` VARCHAR(30) NOT NULL,
  `streetName` VARCHAR(50) NOT NULL,
  `phoneNumber` INT(8) NOT NULL,
  `hasCertificate` BOOLEAN NOT NULL,
  `birthday` DATE NOT NULL,
  `signUpDate` DATE NOT NULL,
  `seniority` DATE NOT NULL,
  `password` VARCHAR(50) NOT NULL,
  `deleted` BOOLEAN NOT NULL,
  `FK_zipCode` INTEGER(4) NOT NULL,
  PRIMARY KEY (`memberID`),
  FOREIGN KEY (`FK_zipCode`) REFERENCES `City` (`zipCode`)
  ON DELETE CASCADE ON UPDATE CASCADE
);

Er der nogen der har et bud?
Tak!