E sad, kako da napravim foreign key relacije? Jer sad kako sam uradio dobijam grešku ERROR 1022 (23000): Can't write; duplicate key in table 'article_category'
CREATE TABLE IF NOT EXISTS `nii`.`article_category` (
`article_id` INT UNSIGNED NOT NULL,
`category_id` MEDIUMINT UNSIGNED NOT NULL,
PRIMARY KEY (`category_id`, `article_id`),
CONSTRAINT `fk_article_id`
FOREIGN KEY (`article_id`)
REFERENCES `nii`.`article` (`id`)
ON DELETE RESTRICT
ON UPDATE CASCADE,
CONSTRAINT `fk_category_id`
FOREIGN KEY (`category_id`)
REFERENCES `nii`.`category` (`id`)
ON DELETE RESTRICT
ON UPDATE CASCADE)
ENGINE = InnoDB