Magento: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '100000001' for key 'UNQ_SALES_FLAT_ORDER_IN

Question

I have installed Magento 1.9.0.1 and I am live since 1 month. The first order of a Client worked without Problem. But now following error message appears when the order should

Answer 1

first check into sales_flat_order table maximum increment_id and change into eav_entity_store table increment_last_id column by incrementing 1 for example your sales_flat_order table maximum increment_id is 100000001 and change eav_entity_store table increment_last_id is 100000002