DELETE FROM {table_prefix}_woocommerce_order_itemmeta;
DELETE FROM {table_prefix}_woocommerce_order_items;
DELETE FROM {table_prefix}_comments WHERE comment_type = 'order_note';
DELETE FROM {table_prefix}_postmeta WHERE post_id IN ( SELECT ID FROM {table_prefix}_posts WHERE post_type = 'shop_order' );
DELETE FROM {table_prefix}_posts WHERE post_type = 'shop_order';