Error
Error Code:
1569
MySQL Error 1569: Auto-Increment Duplicate Entry
Description
This error occurs when an `ALTER TABLE` operation attempts to resequence an `AUTO_INCREMENT` column, but the new sequence would conflict with existing unique key constraints, leading to duplicate entries. It commonly arises when modifying column types, adding columns, or rebuilding tables that have `AUTO_INCREMENT` primary keys or unique indexes.
Error Message
ALTER TABLE causes auto_increment resequencing, resulting in duplicate entry '%s' for key '%s'
Known Causes
3 known causesConflicting Schema Changes
An `ALTER TABLE` statement, such as changing column types or adding unique keys, can trigger an `AUTO_INCREMENT` resequencing that clashes with existing data.
Implicit Table Rebuild
Some `ALTER TABLE` operations implicitly cause the table to be rebuilt, leading to a re-evaluation of `AUTO_INCREMENT` values against unique constraints.
Pre-existing Data Conflicts
The table might already contain data that would become duplicate entries if the `AUTO_INCREMENT` sequence were to be re-generated by the `ALTER` operation.
Solutions
3 solutions available1. Manually Adjust Auto-Increment Counter easy
Directly set the next auto-increment value to avoid collisions.
1
Identify the duplicate entry and the table causing the issue. The error message will usually provide this information.
2
Determine the highest existing `AUTO_INCREMENT` value for the affected table.
SHOW TABLE STATUS LIKE 'your_table_name';
-- Look for the 'Auto_increment' value.3
Calculate the new `AUTO_INCREMENT` value. It should be at least one greater than the highest existing value that is causing the conflict.
4
Alter the table to set the new `AUTO_INCREMENT` value.
ALTER TABLE your_table_name AUTO_INCREMENT = new_auto_increment_value;2. Rebuild the Table with Corrected Data medium
Create a new table, copy data, and then replace the original.
1
Create a new temporary table with the same structure as the problematic table.
CREATE TABLE your_table_name_temp LIKE your_table_name;2
Insert data from the original table into the temporary table, ensuring no duplicate primary keys or unique constraints are violated. You might need to manually adjust or skip problematic rows.
INSERT INTO your_table_name_temp SELECT * FROM your_table_name;3
Drop the original table.
DROP TABLE your_table_name;4
Rename the temporary table to the original table name.
RENAME TABLE your_table_name_temp TO your_table_name;5
After the rename, the `AUTO_INCREMENT` counter should be automatically reset to the next available value.
3. Identify and Remove Conflicting Data medium
Locate and resolve the specific data entries causing the auto-increment conflict.
1
Identify the primary key or unique key that is causing the duplicate entry. The error message should indicate which key is affected.
2
Query the table to find the rows that have the duplicate value for that key.
SELECT your_column_with_duplicate_value, COUNT(*) FROM your_table_name GROUP BY your_column_with_duplicate_value HAVING COUNT(*) > 1;3
Examine the identified duplicate rows. Decide whether to delete the duplicate rows, update them to unique values, or handle them according to your application's logic.
4
Once the duplicates are resolved, you can proceed with your `ALTER TABLE` operation. If the `ALTER TABLE` operation itself was the trigger, you might need to adjust the auto-increment counter afterwards (see Solution 1).