mysql-无法在外键约束中创建表错误

Question

CREATE TABLE IF NOT EXISTS `nm`.`list_activities` (
  `activity_id` INT NOT NULL COMMENT '',
  `activity_name` VARCHAR(45) NULL COMMENT '',
  `activity_type_id` INT NOT NULL COMMENT '',
  PRIMARY KEY (`activity_id`, `activity_type_id`)  COMMENT '',
  CONSTRAINT `fk_list_activities_log`
    FOREIGN KEY (`activity_id`)
    REFERENCES `nm`.`log` (`activity_id`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


CREATE TABLE IF NOT EXISTS `nm`.`log` (
  `date_id` INT NOT NULL COMMENT '',
  `activity_id` INT NOT NULL COMMENT '',
  PRIMARY KEY (`date_id`, `activity_id`)  COMMENT '')
ENGINE = InnoDB;

无法创建list_activities表，它显示错误消息

错误代码：1215。无法添加外键约束

在MySQL中

Answer 1

这是因为您具有复合主键，并且仅在键的一列上创建FK，所以只创建了部分功能依赖项。

PRIMARY KEY (`date_id`, `activity_id`)

   FOREIGN KEY (`activity_id`)
    REFERENCES `nm`.`log` (`activity_id`)

您必须创建一个引用两个键列的FK才能解决此问题。 将您的FK定义更改为

   FOREIGN KEY (`activity_id`, `activity_type_id`)
    REFERENCES `nm`.`log` (`activity_id`, `date_id`)