以下两个address的外键定义是否相同？我的意思是他们是否最终得到了相同的有效database元素（索引，约束等）。我更喜欢后者，因为它是速记而不是输入。

这里明确地创建了地址索引和约束：

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;

约束和索引也是在这里创建的吗？

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;

还有其他差异需要注意吗？