错误代码1833 Cannot change column used in a foreign

最近修改MySQL数据库表中的字段长度时报错，执行更改的sql语句：ALTER TABLE server_list MODIFY COLUMN server_lip CHAR(25);

报错信息： 1 queries executed, 0 success, 1 errors, 0 warnings 查询：alter table server_list modify column server_lip char(25) 错误代码： 1833 Cannot change column 'server_lip': used in a foreign key constraint 'server_history_ibfk_1' of table 'OMServer.server_history'

原因：server_list表中的server_lip字段为server_history表的外键，server_history建表语句： CREATE TABLE server_history ( ID int(11) NOT NULL AUTO_INCREMENT COMMENT '主键ID', history_id int(11) NOT NULL COMMENT '事件ID', history_ip char(15) NOT NULL COMMENT '事件IP地址', history_user char(15) NOT NULL COMMENT '事件用户名', history_datetime datetime NOT NULL COMMENT '事件时间', db_datetime timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '入库时间', history_command char(255) NOT NULL COMMENT '事件命令', PRIMARY KEY (ID), KEY history_ip (history_ip), CONSTRAINT server_history_ibfk_1 FOREIGN KEY (history_ip) REFERENCES server_list (server_lip) ) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8 COMMENT='操作事件表'

解决步骤： 1.锁表 LOCK TABLES server_history WRITE,server_list WRITE; 2.查看是否被锁

3.解除server_history表外键约束 ALTER TABLE server_history DROP FOREIGN KEY server_history_ibfk_1; 4.更改server_list表server_lip字段长度 ALTER TABLE server_list MODIFY COLUMN server_lip CHAR(25); 查看表结构发现已完成字段长度更新

5.新增server_history表外键约束 ALTER TABLE server_history ADD CONSTRAINT server_history_ibfk_1 FOREIGN KEY (history_ip) REFERENCES server_list (server_lip);

6.解除锁定 UNLOCK TABLES;