尝试截断表时出现 MySQL 错误

Question

我在截断 MySQL Server 5.5 上的表时遇到问题。

我试图截断的表有一个列用作另一个表中的外键。

涉及的两个表的CREATE TABLE如下:

CREATE TABLE `tbluser` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(255) NOT NULL,
  `password` varchar(255) NOT NULL,
  `name` varchar(255) NOT NULL,
  `creationDate` datetime NOT NULL,
  `creationUserId` int(11) NOT NULL,
  `updateDate` datetime NOT NULL,
  `updateUserId` int(11) NOT NULL,
  `lastAccess` datetime NOT NULL,
  `enabled` tinyint(1) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `id_UNIQUE` (`id`),
  UNIQUE KEY `email_UNIQUE` (`email`),
  KEY `FK_tbluser_creationUserId` (`creationUserId`),
  KEY `FK_tbluser_updateUserId` (`updateUserId`),
  CONSTRAINT `FK_tbluser_updateUserId` FOREIGN KEY (`updateUserId`) REFERENCES `tbluser` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `FK_tbluser_creationUserId` FOREIGN KEY (`creationUserId`) REFERENCES `tbluser` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;

CREATE TABLE `tblpost` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) NOT NULL,
  `content` mediumtext NOT NULL,
  `creationDate` datetime NOT NULL DEFAULT '1901-01-01 00:00:00',
  `creationUserId` int(11) NOT NULL,
  `updateDate` datetime NOT NULL DEFAULT '1901-01-01 00:00:00',
  `updateUserId` int(11) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `FK_tblpost_creationUserId` (`creationUserId`),
  KEY `FK_tblpost_updateUserId` (`updateUserId`),
  CONSTRAINT `FK_tblpost_updateUserId` FOREIGN KEY (`updateUserId`) REFERENCES `tbluser` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `FK_tblpost_creationUserId` FOREIGN KEY (`creationUserId`) REFERENCES `tbluser` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

请注意，所有约束都设置为DELETE 和UPDATE ON CASCADE。

当我尝试TRUNCATE 表时:

TRUNCATE TABLE `<databasename>`.`tbluser`;

我收到以下错误消息:

Cannot truncate a table referenced in a foreign key constraint
(`<databasename>`.`tblpost`, 
CONSTRAINT `FK_tblpost_updateUserId` 
FOREIGN KEY (`updateUserId`) 
REFERENCES `<databasename>`.`tbluser` (`id`))

除此信息外，还有一个事实是，当在 MySQL Server 5.1 上尝试执行上述操作时，它有效!

有人知道为什么会这样吗？

Answer 1

检查 here . TRUNCATE TABLE 在这种情况下引发错误是有道理的；没有记录的坏事。