MySQL ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
An AUTO_INCREMENT column isn’t indexed (or there are two auto-increment columns).
Seen on:
MySQL
Meaning
MySQL requires the AUTO_INCREMENT column to be part of a key, typically the PRIMARY KEY. Imports that drop keys before adding AUTO_INCREMENT hit this.
Common causes
- AUTO_INCREMENT added before the PRIMARY KEY
- Two AUTO_INCREMENT columns
- Primary key dropped
⚡ Quick fix
- Add PRIMARY KEY (id) in the same statement
- Keep a single auto-increment column
Detailed fix by platform
MySQL
ALTER TABLE items MODIFY id INT UNSIGNED NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY (id);
How to diagnose
- Keys — Is the auto column indexed?
- Recent change — Did it start after a deploy, upgrade, or configuration change? Compare with the last working version.
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Last updated 2 Oct 2026