有趣的问题。您可能需要在调用CREATE TABLE语句之前禁用外键，然后再启用它们。这将允许您直接在CREATE TABLEDDL中定义外键：
例：
SET FOREIGN_KEY_CHECKS = 0;
Query OK, 0 rows affected (0.00 sec)
CREATE TABLE IF NOT EXISTS `rabbits` (
`id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
`name` VARCHAR(255) NOT NULL,
`main_page_id` INT UNSIGNED COMMENT 'What page is the main one',
PRIMARY KEY (`id`),
KEY `main_page_id` (`main_page_id`),
CONSTRAINT `fk_rabbits_main_page` FOREIGN KEY (`main_page_id`) REFERENCES `rabbit_pages` (`id`)
) ENGINE=InnoDB;
Query OK, 0 rows affected (0.04 sec)
CREATE TABLE IF NOT EXISTS `rabbit_pages` (
`id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
`rabbit_id` INT UNSIGNED NOT NULL,
`title` VARCHAR(255) NOT NULL,
`content` TEXT NOT NULL,
PRIMARY KEY (`id`),
KEY `rabbit_id` (`rabbit_id`),
CONSTRAINT `fk_rabbits_pages` FOREIGN KEY (`rabbit_id`) REFERENCES `rabbits` (`id`)
) ENGINE=InnoDB;
Query OK, 0 rows affected (0.16 sec)
SET FOREIGN_KEY_CHECKS = 1;
Query OK, 0 rows affected (0.00 sec)
测试用例：
INSERT INTO rabbits (name, main_page_id) VALUES ('bobby', NULL);
Query OK, 1 row affected (0.02 sec)
INSERT INTO rabbit_pages (rabbit_id, title, content) VALUES (1, 'My Main Page', 'Hello');
Query OK, 1 row affected (0.00 sec)
SELECT * FROM rabbits;
+----+-------+--------------+
| id | name | main_page_id |
+----+-------+--------------+
| 1 | bobby | NULL |
+----+-------+--------------+
1 row in set (0.00 sec)
SELECT * FROM rabbit_pages;
+----+-----------+--------------+---------+
| id | rabbit_id | title | content |
+----+-----------+--------------+---------+
| 1 | 1 | My Main Page | Hello |
+----+-----------+--------------+---------+
1 row in set (0.00 sec)
UPDATE rabbits SET main_page_id = 2 WHERE id = 1;
ERROR 1452 (23000): A foreign key constraint fails
UPDATE rabbits SET main_page_id = 1 WHERE id = 1;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
UPDATE rabbit_pages SET rabbit_id = 2 WHERE id = 1;
ERROR 1452 (23000): A foreign key constraint fails
602392714
清零编程群