# MySQL ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key

**Code:** `1075` · **Category:** MySQL · **Seen on:** MySQL

An AUTO_INCREMENT column isn’t indexed (or there are two auto-increment columns).

## 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

1. Add PRIMARY KEY (id) in the same statement
2. Keep a single auto-increment column

## Detailed fix by platform

### MySQL

1. `ALTER TABLE items MODIFY id INT UNSIGNED NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY (id);`

## How to diagnose

1. **Keys** — Is the auto column indexed?
2. **Recent change** — Did it start after a deploy, upgrade, or configuration change? Compare with the last working version.

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Source: [WhatIsMyError](https://whatismyerror.com/errors/mysql/1075-incorrect-table-definition-auto-column)