Why am I getting MySQL Error 1062: Duplicate entry '0' for key 'PRIMARY' when altering my table?

MySQL Error 1062: Primary Key Duplication '0'

You've encountered an issue while altering the momento_distribution table, receiving the error "1062 - Duplicate entry '0' for key 'PRIMARY'". This could indicate a problem with the data in the table.

The primary key, as defined in your original table structure, was a combination of the momento_id and momento_idmember columns. However, after adding a new id column and setting it as the primary key, you've encountered duplicates in this column, specifically the value '0'.

To resolve this issue, you can try specifying the id column as auto-increment in the table definition, as seen below:

CREATE TABLE `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,
     `id`               INT(11) NOT NULL AUTO_INCREMENT,
     PRIMARY KEY (`id`),  -- New primary key
     KEY `momento_distribution_FI_2` (`momento_idmember`),
     KEY `accepted` (`accepted`, `ext_member`)
  )
ENGINE=InnoDB
DEFAULT CHARSET=latin1;

Alternatively, if you've already created the id column, you can modify it to auto-increment using the following query:

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

By specifying the id column as auto-increment, you ensure that each row has a unique value for this column, eliminating the duplicate '0' issue. This will allow you to alter the table structure and assign the id column as the primary key without losing data.

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