mysql - 一次声明多个外键和单独声明它们有什么区别？

Question

我有一个名为 Order_List 的表，其中包含一个订单列表。每列都包含一个外键，该外键引用订单表中订单的主键。我的问题是，声明这些外键的最佳方式是什么。使用 MySQL Workbench 我发现了两种方法...

方法#1

CREATE  TABLE IF NOT EXISTS 'mydb'.'Order_List' (
    'idOrder_List' INT UNSIGNED NOT NULL AUTO_INCREMENT ,
    'orderID01' INT UNSIGNED NULL ,
    'orderID02' INT UNSIGNED NULL ,
    'orderID03' INT UNSIGNED NULL ,
    'orderID04' INT UNSIGNED NULL ,
    PRIMARY KEY ('idOrder_List') ,
    INDEX 'fk_Order_List_1' ('orderID01' ASC, 'orderID02' ASC, 'orderID03' ASC, 'orderID04' ASC) ,
    CONSTRAINT 'fk_Order_List_1'
      FOREIGN KEY ('orderID01' , 'orderID02' , 'orderID03' , 'orderID04' )
      REFERENCES 'mydb'.'Order' ('idOrder' , 'idOrder' , 'idOrder' , 'idOrder' )
      ON DELETE NO ACTION
      ON UPDATE NO ACTION)
    ENGINE = InnoDB

方法#2

  CREATE  TABLE IF NOT EXISTS 'mydb'.'Order_List' (
    'idOrder_List' INT UNSIGNED NOT NULL AUTO_INCREMENT ,
    'orderID01' INT UNSIGNED NULL ,
    'orderID02' INT UNSIGNED NULL ,
    'orderID03' INT UNSIGNED NULL ,
    'orderID04' INT UNSIGNED NULL ,
    PRIMARY KEY ('idOrder_List') ,
    INDEX 'fk_Order_List_1' ('orderID01' ASC) ,
    INDEX 'fk_Order_List_2' ('orderID02' ASC) ,
    INDEX 'fk_Order_List_3' ('orderID03' ASC) ,
    INDEX 'fk_Order_List_4' ('orderID04' ASC) ,
    CONSTRAINT 'fk_Order_List_1'
      FOREIGN KEY ('orderID01' )
      REFERENCES 'mydb'.'Order' ('idOrder' )
      ON DELETE CASCADE
      ON UPDATE CASCADE,
    CONSTRAINT 'fk_Order_List_2'
      FOREIGN KEY ('orderID02' )
      REFERENCES 'mydb'.'Order' ('idOrder' )
      ON DELETE NO ACTION
      ON UPDATE NO ACTION,
    CONSTRAINT 'fk_Order_List_3'
      FOREIGN KEY ('orderID03' )
      REFERENCES 'mydb'.'Order' ('idOrder' )
      ON DELETE NO ACTION
      ON UPDATE NO ACTION,
    CONSTRAINT 'fk_Order_List_4'
      FOREIGN KEY ('orderID04' )
      REFERENCES 'mydb'.'Order' ('idOrder' )
      ON DELETE NO ACTION
      ON UPDATE NO ACTION)
    ENGINE = InnoDB

第一种方法结合声明。第二种方法将其拆分。哪一个更好？一个比另一个有任何固有的弱点吗？谢谢!

Answer 1

这不是同一个 FK。

• 确保任何 OrderList 行中 4 列的组合存在于 'mydb'.'Order'
中的单个行中
• 另一个确保任何 OrderList 行中的 4 列值独立存在于某些 'mydb'.'Order' 行中的其他值