MySQL 外键错误代码 1215

Question

我在尝试向具有现有表外键的表中添加列时收到错误消息。下面是两个失败的 SQL 语句:

ALTER TABLE current_teams ADD COLUMN master_team_id INT,
ADD FOREIGN KEY fk_master_team_id(master_team_id) REFERENCES master_teams(id) ON DELETE CASCADE;

ALTER TABLE current_teams ADD COLUMN player_id INT,
ADD FOREIGN KEY fk_player_id(player_id) REFERENCES players(id) ON DELETE CASCADE;

我得到的错误是:错误代码:1215。无法添加外键约束

当运行 innodb 时，更详细的消息说:

2016-02-03 17:22:43 0x3210 Error in foreign key constraint of table lod/#sql-1d58_6:FOREIGN KEY fk_master_team_id(master_team_id) REFERENCES master_teams(id) ON DELETE CASCADE: Cannot resolve table name close to: (id) ON DELETE CASCADE

奇怪的是，在其他表上，添加完全相同的外键工作正常。这些语句运行没有问题:

ALTER TABLE team_scouting ADD COLUMN master_team_id INT, 
ADD FOREIGN KEY fk_master_team_id(master_team_id) REFERENCES master_teams(id) ON DELETE CASCADE;
ALTER TABLE team_scouting ADD COLUMN player_id INT, 
ADD FOREIGN KEY fk_player_id(player_id) REFERENCES players(id) ON DELETE CASCADE;

SHOW CREATE TABLE masterteams结果如下:

'CREATE TABLE `master_teams` (
  `team_name` varchar(45) DEFAULT NULL,
  `owner_name` varchar(45) DEFAULT NULL,
  `max_salary` double DEFAULT NULL,
  `penalty` int(11) DEFAULT ''0'',
  `username` varchar(10) DEFAULT NULL,
  `password` varchar(25) DEFAULT NULL,
  `rights` varchar(10) DEFAULT NULL,
  `email` varchar(100) NOT NULL,
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=16 DEFAULT CHARSET=latin1'

仅在此“current_teams”表上添加列/外键失败。任何帮助都会很棒!谢谢。

Answer 1

您的 master_teams 表不是 InnoDB 表，因此 InnoDB 引擎“无法解析”表名。尝试像这样更新它:

ALTER TABLE master_teams ENGINE = InnoDB;

正如 Barmar 在评论中所说，constraint names do need to be globally unique .如果您不指定名称，MySQL 将为您补一个:

If the CONSTRAINTsymbol clause is given, the symbol value, if used, must be unique in the database. A duplicate symbol will result in an error similar to: ERROR 1005 (HY000): Can't create table 'test.#sql-211d_3' (errno: 121). If the clause is not given, or a symbol is not included following the CONSTRAINT keyword, a name for the constraint is created automatically.