Question

我有两个表 - tree_hierarchy：

tree_hierarchy | CREATE TABLE `tree_hierarchy` (
  `tree_id` int(10) unsigned NOT NULL,
  `time_segment` date NOT NULL,
  `parent_node_id` int(10) unsigned NOT NULL,
  `child_node_id` int(10) unsigned NOT NULL,
  PRIMARY KEY (`tree_id`,`time_segment`,`parent_node_id`,`child_node_id`),
  KEY `fk_tree_hierarchy_child_node_idx` (`child_node_id`,`time_segment`),
  KEY `fk_tree_hierarchy_parent_node_idx` (`parent_node_id`,`time_segment`),
  KEY `fk_tree_hierarchy_tree_id_idx` (`tree_id`),
  KEY `fk_tree_hierarchy_child_def` (`time_segment`),
  CONSTRAINT `fk_tree_hierarchy_tree_id` FOREIGN KEY (`tree_id`) REFERENCES `tree` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8

和node_instance：

node_instance | CREATE TABLE `node_instance` (
  `id` int(10) unsigned NOT NULL,
  `node_id` int(10) unsigned NOT NULL,
  `time_segment` date NOT NULL,
  `name` varchar(128) NOT NULL,
  `sharing` enum('Private','Inherited','User','Open') NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `unique_node_ts` (`time_segment`,`node_id`),
  KEY `fk_node_instance_node_1` (`node_id`),
  KEY `fk_node_instance_time_segment_idx` (`time_segment`),
  CONSTRAINT `fk_node_instance_node_id` FOREIGN KEY (`node_id`) REFERENCES `node` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  CONSTRAINT `fk_node_instance_time_segment` FOREIGN KEY (`time_segment`) REFERENCES `time_segment` (`segment`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB DEFAULT CHARSET=utf8

尝试设置约束时：

ALTER TABLE  `tree_hierarchy` ADD CONSTRAINT `fk_tree_hierarchy_child_xyz`
    FOREIGN KEY (`child_node_id` , `time_segment` )
    REFERENCES `node_instance` (`node_id` , `time_segment` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION;

我明白了：

ERROR 1005 (HY000): Can't create table 'empty_structure.#sql-4e8_28b1' (errno: 150)

这意味着我的结构不合适。但我认为两个字段（两个表中的node_id和time_segment都相同）。当我创建简单的约束时，一切都很好：

ALTER TABLE  `tree_hierarchy` ADD CONSTRAINT `fk_tree_hierarchy_child_abcd`
    FOREIGN KEY (`time_segment` )
    REFERENCES `node_instance` (`time_segment` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION;

Query OK, 0 rows affected (0.41 sec)
Records: 0  Duplicates: 0  Warnings: 0

和

ALTER TABLE  `tree_hierarchy` ADD CONSTRAINT `fk_tree_hierarchy_child_efgh`
    FOREIGN KEY (`child_node_id` )
    REFERENCES `node_instance` (`node_id` )
    ON DELETE NO ACTION
    ON UPDATE NO ACTION;

Query OK, 0 rows affected (0.19 sec)
Records: 0  Duplicates: 0  Warnings: 0

我确保外键名称不同（请注意xyz，abcd，efgh后缀）。

前者ADD CONSTRAINT出了什么问题？

Answer 1

一段时间后，我发现在node_instance中我错过了相应的复杂密钥（node_id，time_segment）。相反，我有（time_segment，node_id） - 这就是mysql失败的原因。添加缺失密钥后，一切正常。

mysql服务器无法创建复杂约束

1 个答案: