MySQL错误: Error 1215: Cannot add foreign key constraint

Question

我正在尝试将我的 ERD 正向设计到工作台 6.0 中的方案中，但出现此错误。我检查了所有列类型，它们是相同的。我在这里浏览了类似的问题，但仍然找不到答案。这是错误日志:

xecuting SQL script in server

ERROR: Error 1215: Cannot add foreign key constraint







-- -----------------------------------------------------

-- Table `proj`.`employee`

-- -----------------------------------------------------

CREATE TABLE IF NOT EXISTS `proj`.`employee` (

  `employee_id` INT NOT NULL,

  `position_id` INT NOT NULL,

  PRIMARY KEY (`employee_id`),

  CONSTRAINT `fk_employee_employee_history1`

    FOREIGN KEY (`employee_id`)

    REFERENCES `proj`.`employee_history` (`employee_id`)

    ON DELETE NO ACTION

    ON UPDATE NO ACTION,

  CONSTRAINT `fk_employee_equipment_rentals1`

    FOREIGN KEY (`employee_id`)

    REFERENCES `proj`.`equipment_rentals` (`handling_employee_id`)

    ON DELETE NO ACTION

    ON UPDATE NO ACTION,

  CONSTRAINT `fk_employee_scheduled_trips1`

    FOREIGN KEY (`employee_id`)

    REFERENCES `proj`.`scheduled_trips` (`leader`)

    ON DELETE NO ACTION

    ON UPDATE NO ACTION,

  CONSTRAINT `fk_employee_scheduled_trips2`

    FOREIGN KEY (`employee_id`)

    REFERENCES `proj`.`scheduled_trips` (`assistant`)

    ON DELETE NO ACTION

    ON UPDATE NO ACTION)

ENGINE = InnoDB



SQL script execution finished: statements: 8 succeeded, 1 failed



Fetching back view definitions in final form.

Nothing to fetch

Answer 1

事实证明我的外键约束全部搞砸了。我的关系倒退了。我没有让外键引用主键，而是让主键成为引用非唯一列的外键。我扭转了这一点，并且成功了。