MySql can't make column auto_increment

I have a table "Bestelling" with 4 columns: "Id" (PK), "KlantId", "Datum", "BestellingsTypeId", now I want to make the column Id auto_increment, however, when I try to do that, I get this error:

ERROR 1062: ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '1' for key 'PRIMARY'

SQL Statement:

ALTER TABLE `aafest`.`aafest_bestelling` CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT



ERROR: Error when running failback script. Details follow.



ERROR 1046: No database selected

SQL Statement:

CREATE TABLE `aafest_bestelling` (

  `Id` int(11) NOT NULL,

  `KlantId` int(11) DEFAULT NULL,

  `Datum` date DEFAULT NULL,

  `BestellingstypeId` int(11) DEFAULT NULL,

  PRIMARY KEY (`Id`)

) ENGINE=InnoDB DEFAULT CHARSET=latin1

Anyone got an idea?

Solution 1:

This will happen if the table contains an existing record with an id of 0 (or negative). Updating all existing records to use positive values will allow auto_increment to be set on that column.

Edit: Some people asked how that 0 got in there. For clarification, the MySQL Reference Manual states that "For numeric types, the default is 0, with the exception that for integer or floating-point types declared with the AUTO_INCREMENT attribute, the default is the next value in the sequence." So, if you performed an insert on a table without providing a value for the numeric column before the auto_increment was enabled, then the default 0 would be used during the insert. More details may be found at https://dev.mysql.com/doc/refman/5.0/en/data-type-defaults.html.

Solution 2:

I also had this issue when trying to convert a column to auto_increment where one row had a value of 0. An alternative to changing the 0 value temporarily is via setting:

SET SESSION sql_mode='NO_AUTO_VALUE_ON_ZERO';

for the session.

This allowed the column to be altered to auto_increment with the zero id in place.

The zero isn't ideal - and I also wouldn't recommend it being used in an auto_increment column. Unfortunately it's part of an inherited data set so I'm stuck with it for now.

Best to clear the setting (and any others) afterwards with:

SET SESSION sql_mode='';

although it will be cleared when the current client session clsoes.

Full details on the 'NO_AUTO_VALUE_ON_ZERO' setting here.

Solution 3:

This happens when MySQL can not determine a proper auto_increment value. In your case, MySQL choose 1 as next auto_increment value, however there is already row with that value in the table.

One way to resolve the issue is to choose a proper auto_increment value yourself:

ALTER TABLE ... CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT = 123456;

(Note the AUTO_INCREMENT=123456 at the end.)

Solution 4:

The easiest way that I have found to solve this issue is to first set the table's AUTO INCREMENT value before altering the column. Just make sure that you set the auto increment value higher than the largest value currently in that column:

ALTER TABLE `aafest`.`aafest_bestelling` 
AUTO_INCREMENT = 100, 
CHANGE COLUMN `Id` `Id` INT(11) NOT NULL AUTO_INCREMENT

I tested this on MySQL 5.7 and it worked great for me.