sql - 删除带有自引用外键的行

Question

我有一个 MySQL 表，其定义如下:

CREATE TABLE `guestbook` (
  `Id` int(10) unsigned NOT NULL,
  `ThreadId` int(10) unsigned NOT NULL,
  PRIMARY KEY (`Id`),
  KEY `ThreadId` (`ThreadId`),
  CONSTRAINT `guestbook_ibfk_1` FOREIGN KEY (`ThreadId`) REFERENCES `guestbook` (`Id`)
) ENGINE=InnoDB;

目前表中只有 1 行:

mysql> select * from guestbook;
+-----+----------+
| Id  | ThreadId |
+-----+----------+
| 211 |      211 |
+-----+----------+

问题是没有办法在不破坏约束的情况下删除这一行。

mysql> delete from guestBook;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`polaris`.`guestbook`, CONSTRAINT `guestbook_ibfk_1` FOREIGN KEY (`ThreadId`) REFERENCES `guestbook` (`Id`))

由于 ThreadId 列定义为不为空，因此也不可能临时将 ThreadId 设置为不同的值来删除该行。有没有办法在不更改表定义或删除整个表的情况下删除行？

Answer 1

您可以使用此查询暂时禁用外键约束:

SET foreign_key_checks = 0;