MySQL-尝试添加新列时出现重复输入错误 [英] MySQL - Duplicate entry error when trying to add new column
本文介绍了MySQL-尝试添加新列时出现重复输入错误的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个MySQL数据库,其中的表使用innodb引擎具有200万行.我想添加另一列,但仍然出现以下错误:
I have a MySQL database with a table that has 2 million rows using innodb engine. I want to add another column, but I keep getting the following error:
Error 1062: Duplicate entry '' for key 'PRIMARY' SQL Statement: ALTER TABLE `mydb`.`table` ADD COLUMN `country` VARCHAR(35) NULL DEFAULT NULL AFTER `email`
如何添加列而不出现此错误?
How can I add the column without getting this error?
编辑:表定义
id int(11) NOT NULL AUTO_INCREMENT,
user_id varchar(45) NOT NULL,
first_name varchar(150) DEFAULT NULL,
last_name varchar(150) DEFAULT NULL,
gender varchar(10) DEFAULT NULL,
email varchar(100) DEFAULT NULL,
created_at bigint(20) DEFAULT NULL,
updated_at bigint(20) DEFAULT NULL,
PRIMARY KEY (`id`,`user_id`),
UNIQUE KEY `user_id_UNIQUE` (`user_id`),
KEY `first_name` (`first_name`),
KEY `last_name` (`last_name`)
编辑#2:显示索引输出
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Index_type
table 0 PRIMARY 1 id A 3516446 BTREE
table 0 PRIMARY 2 user_id A 3516446 BTREE
table 0 user_id_UNIQUE 1 user_id A 3516446 BTREE
table 1 first_name 1 first_name A 390716 BTREE
table 1 last_name 1 last_name A 439555 BTREE
推荐答案
它的解决方案将在写时锁定表,但通常适合解决表不是很大的问题
it solution will lock table on write, but often suitable for solving the problem if table is not very big
LOCK TABLES my_table WRITE;
ALTER TABLE my_table
ADD COLUMN `ts` DATETIME NULL AFTER `id`;
UNLOCK TABLES;
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