Mysql 错误代码1215是否具有相同的数据类型？

有人能解释一下为什么我总是犯这个错误吗？它们是相同的数据类型…

当你问问题时，应该更具体一些。您有八个外键，您至少应该说是哪一个导致了错误

最好将您的问题简化为错误中涉及的两个表格：顶点和委员会

我看到的是：

CREATE SCHEMA IF NOT EXISTS `cap` DEFAULT CHARACTER SET utf8 ;
USE `cap` ;

-- -----------------------------------------------------
-- Table `capstone`.`users`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`users` (
  `username` VARCHAR(45) NOT NULL,
  `password` VARCHAR(100) NOT NULL,
  `roleid` INT NOT NULL,
  `fullname` VARCHAR(45) NOT NULL,
  `email` VARCHAR(45) NULL,
  `phone` VARCHAR(45) NULL,
  `department` VARCHAR(45) NULL,
  PRIMARY KEY (`username`, `roleid`))
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`capstone`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`capstone` (
  `username` VARCHAR(45) NOT NULL,
  `capstoneid` INT NOT NULL,
  `typeid` INT NOT NULL,
  `title` VARCHAR(45) NULL,
  `abstract` MEDIUMTEXT NULL,
  `plagerismscore` VARCHAR(45) NULL,
  `grade` VARCHAR(45) NULL,
  PRIMARY KEY (`username`, `capstoneid`, `typeid`),
  INDEX `fk_capstone_users_idx` (`username` ASC),
  CONSTRAINT `fk_capstone_users`
    FOREIGN KEY (`username`)
    REFERENCES `cap`.`users` (`username`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`committee`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`committee` (
  `capstoneid` INT NOT NULL,
  `username` VARCHAR(45) NOT NULL,
  `has_accepted` TINYINT NULL,
  `has_declined` TINYINT NULL,
  `positionid` INT NOT NULL,
  `tracking` TINYINT NULL,
  PRIMARY KEY (`capstoneid`, `username`, `positionid`),
  CONSTRAINT `fk_committee_capstone`
    FOREIGN KEY (`capstoneid`)
    REFERENCES `cap`.`capstone` (`capstoneid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`studentdetails`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`studentdetails` (
  `username` VARCHAR(45) NOT NULL,
  `mastersstart` VARCHAR(45) NULL,
  `capstonestart` VARCHAR(45) NULL,
  PRIMARY KEY (`username`),
  CONSTRAINT `fk_studentdetails_users`
    FOREIGN KEY (`username`)
    REFERENCES `cap`.`users` (`username`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`ritcalendar`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`ritcalendar` (
  `term` INT NOT NULL,
  `startdate` VARCHAR(45) NULL,
  `adddropdeadline` VARCHAR(45) NULL,
  `gradedeadline` VARCHAR(45) NULL,
  `enddate` VARCHAR(45) NULL,
  PRIMARY KEY (`term`))
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`statushistory`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`statushistory` (
  `capstoneid` INT NOT NULL,
  `statusid` INT NOT NULL,
  `date` DATETIME(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`capstoneid`, `statusid`),
  UNIQUE INDEX `capstoneid_UNIQUE` (`capstoneid` ASC),
  CONSTRAINT `fk_statushistory_capstone`
    FOREIGN KEY (`capstoneid`)
    REFERENCES `cap`.`capstone` (`capstoneid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`status`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`status` (
  `statusid` INT NOT NULL,
  `name` VARCHAR(45) NULL,
  `stepcode` VARCHAR(45) NULL,
  `description` VARCHAR(255) NULL,
  PRIMARY KEY (`statusid`),
  CONSTRAINT `fk_status_statushistory`
    FOREIGN KEY (`statusid`)
    REFERENCES `cap`.`statushistory` (`statusid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`roles`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`roles` (
  `roleid` INT NOT NULL,
  `role` VARCHAR(10) NOT NULL,
  PRIMARY KEY (`roleid`),
  UNIQUE INDEX `role_UNIQUE` (`role` ASC),
  CONSTRAINT `fk_roles_users`
    FOREIGN KEY (`roleid`)
    REFERENCES `cap`.`users` (`roleid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`types`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`types` (
  `typeid` INT NOT NULL,
  `type` VARCHAR(45) NOT NULL,
  PRIMARY KEY (`typeid`),
  CONSTRAINT `fk_types_capstone`
    FOREIGN KEY (`typeid`)
    REFERENCES `cap`.`capstone` (`typeid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


-- -----------------------------------------------------
-- Table `capstone`.`positions`
-- -----------------------------------------------------
CREATE TABLE IF NOT EXISTS `cap`.`positions` (
  `positionid` INT NOT NULL,
  `position` VARCHAR(45) NULL,
  PRIMARY KEY (`positionid`),
  CONSTRAINT `fk_postions_committee`
    FOREIGN KEY (`positionid`)
    REFERENCES `cap`.`committee` (`positionid`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB;


CREATE TABLE IF NOT EXISTS `cap`.`committee` (   `capstoneid` INT NOT NULL,   `username` VARCHAR(45) NOT NULL,   `has_accepted` TINYINT NULL,   `has_declined` TINYINT NULL,   `positionid` INT NOT NULL,   `tracking` TINYINT NULL,   PRIMARY KEY (`capstoneid`, `username`, `positionid`),   CONSTRAINT `fk_committee_capstone`     FOREIGN KEY (`capstoneid`)     REFERENCES `cap`.`capstone` (`capstoneid`)     ON DELETE NO ACTION     ON UPDATE NO ACTION) ENGINE = InnoDB    Error Code: 1215. Cannot add foreign key constraint 0.031 sec

在

委员会

中有一个FK，它引用了

顶点

中三列主键的中间列

---

您应该始终使FK与它引用的主键具有相同的列。

请指出您从何处获得错误以及完整的错误消息。

CREATE TABLE IF NOT EXISTS `cap`.`capstone` (
  ...
  PRIMARY KEY (`username`, `capstoneid`, `typeid`),

CREATE TABLE IF NOT EXISTS `cap`.`committee` (
  ...
    FOREIGN KEY (`capstoneid`)
    REFERENCES `cap`.`capstone` (`capstoneid`)