Magento permet d’annuler une commande, mais ne propose pas la possibilité de supprimer une commande qu’elle soit terminée ou non. Cela est utile pour supprimer les commandes de test sans pour autant supprimer toutes les commandes de Magento.

Pour cela direction la base de données afin d’agir directement sur celle-ci :

-- Renseigner votre numéro de commande ici
SET @increment_id = 100000025;
-- Récupère l'id de la commande en interne
SELECT @order_id := entity_id FROM sales_order WHERE increment_id = @increment_id;
-- Supprime la commande
DELETE FROM sales_order WHERE entity_id = @order_id;
-- Supprime tous les enregistrements en relation avec la commande
DELETE FROM sales_order_entity WHERE parent_id = @order_id;
-- Supprime les factures, remboursement, expéditions en relation avec la commande
DELETE s FROM sales_order_entity s
 JOIN sales_order_entity_int si on s.entity_id = si.entity_id
 JOIN eav_attribute a on si.attribute_id = a.attribute_id
 WHERE
 a.attribute_code = 'order_id'
 AND si.value = @order_id;
-- Supprime les enregistrements dans la tables des produits commandés
DELETE FROM sales_flat_order_item WHERE order_id=@order_id;

[Source : http://www.magexpert.com/2010/02/comment-supprimer-une-commande-terminee-dans-magento/]

Exécuter la commande SQL suivante :

Attention, cela supprime aussi les clients de test !

Magento >= 1.4.*.* :

TRUNCATE  `customer_address_entity` ;
ALTER TABLE customer_address_entity AUTO_INCREMENT=0;
TRUNCATE  `customer_address_entity_datetime` ;
ALTER TABLE customer_address_entity_datetime AUTO_INCREMENT=0;
TRUNCATE  `customer_address_entity_decimal` ;
ALTER TABLE customer_address_entity_decimal AUTO_INCREMENT=0;
TRUNCATE  `customer_address_entity_int` ;
ALTER TABLE customer_address_entity_int AUTO_INCREMENT=0;
TRUNCATE  `customer_address_entity_text` ;
ALTER TABLE customer_address_entity_text AUTO_INCREMENT=0;
TRUNCATE  `customer_address_entity_varchar` ;
ALTER TABLE customer_address_entity_varchar AUTO_INCREMENT=0;
TRUNCATE  `customer_entity` ;
ALTER TABLE customer_entity AUTO_INCREMENT=0;
TRUNCATE  `customer_entity_datetime` ;
ALTER TABLE customer_entity_datetime AUTO_INCREMENT=0;
TRUNCATE  `customer_entity_decimal` ;
ALTER TABLE customer_entity_decimal AUTO_INCREMENT=0;
TRUNCATE  `customer_entity_int` ;
ALTER TABLE customer_entity_int AUTO_INCREMENT=0;
TRUNCATE  `customer_entity_text` ;
ALTER TABLE customer_entity_text AUTO_INCREMENT=0;
TRUNCATE  `customer_entity_varchar` ;
ALTER TABLE customer_entity_varchar AUTO_INCREMENT=0;
TRUNCATE  `eav_entity_store` ;
ALTER TABLE eav_entity_store AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order` ;
ALTER TABLE sales_flat_order AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order_address` ;
ALTER TABLE sales_flat_order_address AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order_grid` ;
ALTER TABLE sales_flat_order_grid AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order_item` ;
ALTER TABLE sales_flat_order_item AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order_payment` ;
ALTER TABLE sales_flat_order_payment AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_order_status_history` ;
ALTER TABLE sales_flat_order_status_history AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote` ;
ALTER TABLE sales_flat_quote AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_address` ;
ALTER TABLE sales_flat_quote_address AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_address_item` ;
ALTER TABLE sales_flat_quote_address_item AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_item` ;
ALTER TABLE sales_flat_quote_item AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_item_option` ;
ALTER TABLE sales_flat_quote_item_option AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_payment` ;
ALTER TABLE sales_flat_quote_payment AUTO_INCREMENT=0;
TRUNCATE  `sales_flat_quote_shipping_rate` ;
ALTER TABLE sales_flat_quote_shipping_rate AUTO_INCREMENT=0;
TRUNCATE  `sales_order_tax` ;
ALTER TABLE sales_order_tax AUTO_INCREMENT=0;

Source

Magento < 1.4 :

DELETE FROM sales_flat_order_item;
DELETE FROM sales_flat_quote;
DELETE FROM sales_flat_quote_address;
DELETE FROM sales_flat_quote_address_item;
DELETE FROM sales_flat_quote_item;
DELETE FROM sales_flat_quote_item_option;
DELETE FROM sales_flat_quote_payment;
DELETE FROM sales_flat_quote_shipping_rate;
DELETE FROM sales_order;
DELETE FROM sales_order_datetime;
DELETE FROM sales_order_decimal;
DELETE FROM sales_order_entity;
DELETE FROM sales_order_entity_datetime;
DELETE FROM sales_order_entity_decimal;
DELETE FROM sales_order_entity_int;
DELETE FROM sales_order_entity_text;
DELETE FROM sales_order_entity_varchar;
DELETE FROM sales_order_int;
DELETE FROM sales_order_tax;
DELETE FROM sales_order_text;
DELETE FROM sales_order_varchar;
DELETE FROM eav_entity_store;

Note : Article à part pour la suppression d’une commande spécifique dans Magento