MySQL 1062 - Duplicate entry '0' for key 'PRIMARY'

Question

I have the following table in MySQL version 5.5.24

DROP TABLE IF EXISTS `momento_distribution`;

CREATE TABLE IF NOT EXISTS `momento_distribution`
  (
     `momento_id`       INT(11) NOT NULL,
     `momento_idmember` INT(11) NOT NULL,
     `created_at`       DATETIME DEFAULT NULL,
     `updated_at`       DATETIME DEFAULT NULL,
     `unread`           TINYINT(1) DEFAULT '1',
     `accepted`         VARCHAR(10) NOT NULL DEFAULT 'pending',
     `ext_member`       VARCHAR(255) DEFAULT NULL,
     PRIMARY KEY (`momento_id`, `momento_idmember`),
     KEY `momento_distribution_FI_2` (`momento_idmember`),
     KEY `accepted` (`accepted`, `ext_member`)
  )
ENGINE=InnoDB
DEFAULT CHARSET=latin1;

It has lots of data with many-to-one relations with two other tables with ondelete=restrict and onupdate=restrict.

Now, I need to change the structure and introduce separate primary key in the table, while still keeping existing relations and data. For that, I executed the following query:

ALTER TABLE  `momento_distribution` ADD  `id` INT( 11 ) NOT NULL FIRST;
ALTER TABLE  `momento_distribution` DROP PRIMARY KEY , ADD PRIMARY KEY (  `id` );

Unfortunately, my second query failed with the following error:

1062 - Duplicate entry '0' for key 'PRIMARY'

Can someone please point out the issue? I guess that the issue is the existing relation, but I don't want to lose the existing relation or data, that has several thousand rows. Is there any way to do this without losing data?

EDIT: By viewing data, I got that the newly created column has the value '0' in it. Probably this is not allowing to change the Primary Key due to duplicate records (in new Primary Key)

I have more than 8,000 rows, so I can't change it manually. Is there any way to assign rowid to a new Primary Key?

Answer 1

You need to specify the primary key as auto-increment

CREATE TABLE `momento_distribution`
  (
     `momento_id`       INT(11) NOT NULL AUTO_INCREMENT,
     `momento_idmember` INT(11) NOT NULL,
     `created_at`       DATETIME DEFAULT NULL,
     `updated_at`       DATETIME DEFAULT NULL,
     `unread`           TINYINT(1) DEFAULT '1',
     `accepted`         VARCHAR(10) NOT NULL DEFAULT 'pending',
     `ext_member`       VARCHAR(255) DEFAULT NULL,
     PRIMARY KEY (`momento_id`, `momento_idmember`),
     KEY `momento_distribution_FI_2` (`momento_idmember`),
     KEY `accepted` (`accepted`, `ext_member`)
  )
ENGINE=InnoDB
DEFAULT CHARSET=latin1$$

With regards to comment below, how about:

ALTER TABLE `momento_distribution`
  CHANGE COLUMN `id` `id` INT(11) NOT NULL AUTO_INCREMENT,
  DROP PRIMARY KEY,
  ADD PRIMARY KEY (`id`);

A PRIMARY KEY is a unique index, so if it contains duplicates, you cannot assign the column to be unique index, so you may need to create a new column altogether