How to delete Magento order programmatically

Unfortunately, there is no way in Magento to delete the orders from Magento store.
You can only process and set status as "Cancelled" of these orders but you can’t really delete those orders from your Magento store.
In order to delete these orders, you have to log in to your PhpmyAdmin and run some queries to get rid of those orders.

Delete a single order:

You need to run the following query on your database:

  set @increment_id='00000111';
  select @order_id:=entity_id from prefix_sales_order_entity where increment_id=@increment_id;
  delete from prefix_sales_order_entity where entity_id=@order_id or parent_id=@order_id;
  delete from prefix_sales_order where increment_id=@increment_id;
 
In the above example, we deleted order '#00000111'. Generally people use prefix to database tables, so change the "prefix_" in the above query with the prefix you have chosen for your store.

Delete all Magento orders:

You need to run the following query on your database:
 
  SET FOREIGN_KEY_CHECKS=0;

  TRUNCATE `sales_order`;
  TRUNCATE `sales_order_datetime`;
  TRUNCATE `sales_order_decimal`;
  TRUNCATE `sales_order_entity`;
  TRUNCATE `sales_order_entity_datetime`;
  TRUNCATE `sales_order_entity_decimal`;
  TRUNCATE `sales_order_entity_int`;
  TRUNCATE `sales_order_entity_text`;
  TRUNCATE `sales_order_entity_varchar`;
  TRUNCATE `sales_order_int`;
  TRUNCATE `sales_order_text`;
  TRUNCATE `sales_order_varchar`;
  TRUNCATE `sales_flat_quote`;
  TRUNCATE `sales_flat_quote_address`;
  TRUNCATE `sales_flat_quote_address_item`;
  TRUNCATE `sales_flat_quote_item`;
  TRUNCATE `sales_flat_quote_item_option`;
  TRUNCATE `sales_flat_order_item`;
  TRUNCATE `sendfriend_log`;
  TRUNCATE `tag`;
  TRUNCATE `tag_relation`;
  TRUNCATE `tag_summary`;
  TRUNCATE `wishlist`;
  TRUNCATE `log_quote`;
  TRUNCATE `report_event`;

  ALTER TABLE `sales_order` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_datetime` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_decimal` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity_datetime` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity_decimal` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity_int` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity_text` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_entity_varchar` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_int` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_text` AUTO_INCREMENT=1;
  ALTER TABLE `sales_order_varchar` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_quote` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_quote_address` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_quote_address_item` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_quote_item` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_quote_item_option` AUTO_INCREMENT=1;
  ALTER TABLE `sales_flat_order_item` AUTO_INCREMENT=1;
  ALTER TABLE `sendfriend_log` AUTO_INCREMENT=1;
  ALTER TABLE `tag` AUTO_INCREMENT=1;
  ALTER TABLE `tag_relation` AUTO_INCREMENT=1;
  ALTER TABLE `tag_summary` AUTO_INCREMENT=1;
  ALTER TABLE `wishlist` AUTO_INCREMENT=1;
  ALTER TABLE `log_quote` AUTO_INCREMENT=1;
  ALTER TABLE `report_event` AUTO_INCREMENT=1;

  -- lets reset customers
  TRUNCATE `customer_address_entity`;
  TRUNCATE `customer_address_entity_datetime`;
  TRUNCATE `customer_address_entity_decimal`;
  TRUNCATE `customer_address_entity_int`;
  TRUNCATE `customer_address_entity_text`;
  TRUNCATE `customer_address_entity_varchar`;
  TRUNCATE `customer_entity`;
  TRUNCATE `customer_entity_datetime`;
  TRUNCATE `customer_entity_decimal`;
  TRUNCATE `customer_entity_int`;
  TRUNCATE `customer_entity_text`;
  TRUNCATE `customer_entity_varchar`;
  TRUNCATE `log_customer`;
  TRUNCATE `log_visitor`;
  TRUNCATE `log_visitor_info`;

  ALTER TABLE `customer_address_entity` AUTO_INCREMENT=1;
  ALTER TABLE `customer_address_entity_datetime` AUTO_INCREMENT=1;
  ALTER TABLE `customer_address_entity_decimal` AUTO_INCREMENT=1;
  ALTER TABLE `customer_address_entity_int` AUTO_INCREMENT=1;
  ALTER TABLE `customer_address_entity_text` AUTO_INCREMENT=1;
  ALTER TABLE `customer_address_entity_varchar` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity_datetime` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity_decimal` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity_int` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity_text` AUTO_INCREMENT=1;
  ALTER TABLE `customer_entity_varchar` AUTO_INCREMENT=1;
  ALTER TABLE `log_customer` AUTO_INCREMENT=1;
  ALTER TABLE `log_visitor` AUTO_INCREMENT=1;
  ALTER TABLE `log_visitor_info` AUTO_INCREMENT=1;

  -- Now, lets Reset all ID counters
  TRUNCATE `eav_entity_store`;
  ALTER TABLE  `eav_entity_store` AUTO_INCREMENT=1;

  SET FOREIGN_KEY_CHECKS=1;