Mysql组合键出外组合键

Question

我试图在 Mysql WorkBench 中的两个表之间建立多对多关系，而这两个表中的一个具有复合主键（部分来自 2 个外键）。当我尝试生成 SQL 时，出现此错误：

错误：错误 1215：无法添加外键约束

SQL 代码：

    -- -----------------------------------------------------
    -- Table `A_D_schema`.`Resources_has_OwnerGroups`
    -- -----------------------------------------------------
    CREATE TABLE IF NOT EXISTS `A_D_schema`.`Resources_has_OwnerGroups` (
      `Resources_id` INT NOT NULL,
      `OwnerGroups_id` INT NOT NULL,
      `OwnerGroups_Instances_has_Customers_Instances_idInstances` INT NOT NULL,
      `OwnerGroups_Instances_has_Customers_Customers_idCustomers` INT NOT NULL,
      PRIMARY KEY (`Resources_id`, `OwnerGroups_id`, `OwnerGroups_Instances_has_Customers_Instances_idInstances`, `OwnerGroups_Instances_has_Customers_Customers_idCustomers`),
      INDEX `fk_Resources_has_OwnerGroups_OwnerGroups1_idx` (`OwnerGroups_id` ASC, `OwnerGroups_Instances_has_Customers_Instances_idInstances` ASC, `OwnerGroups_Instances_has_Customers_Customers_idCustomers` ASC),
      INDEX `fk_Resources_has_OwnerGroups_Resources1_idx` (`Resources_id` ASC),
      CONSTRAINT `fk_Resources_has_OwnerGroups_Resources1`
        FOREIGN KEY (`Resources_id`)
        REFERENCES `A_D_schema`.`Resources` (`id`)
        ON DELETE NO ACTION
        ON UPDATE NO ACTION,
      CONSTRAINT `fk_Resources_has_OwnerGroups_OwnerGroups1`
        FOREIGN KEY (`OwnerGroups_id` , `OwnerGroups_Instances_has_Customers_Instances_idInstances` , `OwnerGroups_Instances_has_Customers_Customers_idCustomers`)
        REFERENCES `A_D_schema`.`OwnerGroups` (`id` , `Instances_has_Customers_Instances_idInstances` , `Instances_has_Customers_Customers_idCustomers`)
        ON DELETE NO ACTION
        ON UPDATE NO ACTION)
    ENGINE = InnoDB

从SHOW ENGINE INNODB STATUS我可以看到这条消息：

Cannot resolve column name close to:
)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_Resources_has_OwnerGroups_OwnerGroups1`
    FOREIGN KEY (`OwnerGroups_id` , `OwnerGroups_Instances_has_Customers_Instances_idInstances` , `OwnerGroups_Instances_has_Customers_Customers_idCustomers`)
    REFERENCES `A_D_schema`.`OwnerGroups` (`id` , `Instances_has_Customers_Instances_idInstances` , `Instances_has_Customers_Customers_idCustomers`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION)
ENGINE = InnoDB

SHOW CREATE TABLE Resources 和 SHOW CREATE TABLE OwnerGroups：

CREATE TABLE `Resources` (
  `idResources` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(45) DEFAULT NULL,
  `role` int(11) DEFAULT NULL COMMENT 'role : 1 disptcher \n0 admin',
  PRIMARY KEY (`idResources`),
  UNIQUE KEY `idresources_UNIQUE` (`idResources`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

CREATE TABLE `OwnerGroups` (
  `idOwnerGroups` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(45) DEFAULT NULL,
  `group` int(11) DEFAULT NULL,
  PRIMARY KEY (`idOwnerGroups`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Answer 1

  CONSTRAINT `fk_Resources_has_OwnerGroups_Resources1`
    FOREIGN KEY (`Resources_id`)
    REFERENCES `A_D_schema`.`Resources` (`id`)

您的资源表没有id 列。它的主键是idResources。

  CONSTRAINT `fk_Resources_has_OwnerGroups_OwnerGroups1`
    FOREIGN KEY (`OwnerGroups_id` , `OwnerGroups_Instances_has_Customers_Instances_idInstances` , `OwnerGroups_Instances_has_Customers_Customers_idCustomers`)
    REFERENCES `A_D_schema`.`OwnerGroups` (`id` , `Instances_has_Customers_Instances_idInstances` , `Instances_has_Customers_Customers_idCustomers`)

您的 OwnerGroups 表没有 id 列。它的主键是idOwnerGroups。它根本没有您引用的其他两列。

---

一般来说，当你声明一个外键时，首先你命名子表中的列：

CREATE TABLE Child (
  childCol1 INT,
  childCol2 INT,
...
FOREIGN KEY (childCol1, childCol2) ...

然后你引用父表中的列：

... REFERENCES Parent (parentCol1, parentCol2)
);

您必须使用列名，因为它们存在于父表中。

您在父表中引用的列必须一起是该表的 PRIMARY KEY 或 UNIQUE KEY。换句话说，鉴于上面的示例，它不适用于此 Parent 表：

CREATE TABLE Parent (
  parentCol1 INT,
  parentCol2 INT,
  PRIMARY KEY (parentCol1)
);

因为 PRIMARY KEY 不包括 parentCol2。

---

在你的情况下，以下应该有效：

CREATE TABLE IF NOT EXISTS `A_D_schema`.`Resources_has_OwnerGroups` (
  `Resources_id` INT NOT NULL,
  `OwnerGroups_id` INT NOT NULL,
  `OwnerGroups_Instances_has_Customers_Instances_idInstances` INT NOT NULL,
  `OwnerGroups_Instances_has_Customers_Customers_idCustomers` INT NOT NULL,
  PRIMARY KEY (`Resources_id`, `OwnerGroups_id`, `OwnerGroups_Instances_has_Customers_Instances_idInstances`, `OwnerGroups_Instances_has_Customers_Customers_idCustomers`),
  CONSTRAINT `fk_Resources_has_OwnerGroups_Resources1`
    FOREIGN KEY (`Resources_id`)
    REFERENCES `A_D_schema`.`Resources` (`idResources`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION,
  CONSTRAINT `fk_Resources_has_OwnerGroups_OwnerGroups1`
    FOREIGN KEY (`OwnerGroups_id`)
    REFERENCES `A_D_schema`.`OwnerGroups` (`idOwnerGroups`)
    ON DELETE NO ACTION
    ON UPDATE NO ACTION
) ENGINE = InnoDB

我删除了几个冗余的 INDEX 定义。您不需要索引 PRIMARY KEY，它已经是表的聚集索引。您不需要为在外键声明中使用的列建立索引，如果需要，MySQL 会自动为该列建立索引（尽管如果该列已经存在索引，则 FK 约束将使用该索引）。

我不确定我是否理解您的另外两列 OwnerGroups_Instances_has_Customers_Instances_idInstances 和 OwnerGroups_Instances_has_Customers_Customers_idCustomers 的用途。通常在多对多表中，您只需要足够的列来引用各个父表的主键。

---

你的评论：

您应该不时尝试刷新架构视图。在“SCHEMAS”的右侧有一个带有一对弯曲箭头的按钮。