这些 FK 定义是否等价？

Question

下面两个address的外键定义是否等价？我的意思是它们最终是否具有相同的有效数据库元素（索引、约束等）。我更喜欢后者，因为它是 shorthand 并且输入更少。

此处显式创建地址索引和约束：

CREATE TABLE customer (
  customer_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
  first_name VARCHAR(45) NOT NULL,
  last_name VARCHAR(45) NOT NULL,
  PRIMARY KEY  (customer_id),
  KEY idx_fk_address_id (address_id),
  CONSTRAINT fk_customer_address FOREIGN KEY (address_id) REFERENCES address (address_id) ON DELETE RESTRICT ON UPDATE CASCADE
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

这里是否也创建了约束和索引？

CREATE TABLE customer (
  customer_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
  first_name VARCHAR(45) NOT NULL,
  last_name VARCHAR(45) NOT NULL,
  PRIMARY KEY  (customer_id),
  FOREIGN KEY (address_id) REFERENCES address (address_id) ON DELETE RESTRICT ON UPDATE CASCADE
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

还有其他需要注意的区别吗？

Answer 1

从功能的角度来看，这些声明是等效的。不同之处在于第一个代码片段设置了一个便于以后维护的友好名称，第二个代码片段将创建一些 auto-generated 名称。

这些 FK 定义是否等价？

Are these FK definitions equivalent?

mysql

sql

schema

ddl

foreign-keys