We have tested the queries below in :

WooCommerce version: 3.5.7
WordPress version: 5.1.1

( Use at own risk )

=======================

Delete all orders woocommerce

DELETE FROM wp_woocommerce_order_itemmeta;
DELETE FROM wp_woocommerce_order_items;
DELETE FROM wp_comments WHERE comment_type = 'order_note';
DELETE FROM wp_postmeta WHERE post_id IN ( SELECT ID FROM wp_posts WHERE post_type = 'shop_order' );
DELETE FROM wp_posts WHERE post_type = 'shop_order';

==========================

delete all products

DELETE relations., taxes., terms.*
FROM wp_term_relationships AS relations
INNER JOIN wp_term_taxonomy AS taxes
ON relations.term_taxonomy_id=taxes.term_taxonomy_id
INNER JOIN wp_terms AS terms
ON taxes.term_id=terms.term_id
WHERE object_id IN (SELECT ID FROM wp_posts WHERE post_type='product');
DELETE FROM wp_postmeta WHERE post_id IN (SELECT ID FROM wp_posts WHERE post_type = 'product');
DELETE FROM wp_posts WHERE post_type = 'product';

==========================

Remove all attributes from WooCommerce

DELETE FROM wp_terms WHERE term_id IN (SELECT term_id FROM wp_term_taxonomy WHERE taxonomy LIKE 'pa_%');
DELETE FROM wp_term_taxonomy WHERE taxonomy LIKE 'pa_%';
DELETE FROM wp_term_relationships WHERE term_taxonomy_id not IN (SELECT term_taxonomy_id FROM wp_term_taxonomy);

==========================

Delete all WooCommerce products (2)

DELETE FROM wp_term_relationships WHERE object_id IN (SELECT ID FROM wp_posts WHERE post_type IN ('product','product_variation'));
DELETE FROM wp_postmeta WHERE post_id IN (SELECT ID FROM wp_posts WHERE post_type IN ('product','product_variation'));
DELETE FROM wp_posts WHERE post_type IN ('product','product_variation');

==========================

Delete orphaned postmeta

DELETE pm
FROM wp_postmeta pm
LEFT JOIN wp_posts wp ON wp.ID = pm.post_id
WHERE wp.ID IS NULL;

==========================

delete all categories

DELETE a,c FROM wp_terms AS a
LEFT JOIN wp_term_taxonomy AS c ON a.term_id = c.term_id
LEFT JOIN wp_term_relationships AS b ON b.term_taxonomy_id = c.term_taxonomy_id
WHERE c.taxonomy = 'product_tag';
DELETE a,c FROM wp_terms AS a
LEFT JOIN wp_term_taxonomy AS c ON a.term_id = c.term_id
LEFT JOIN wp_term_relationships AS b ON b.term_taxonomy_id = c.term_taxonomy_id
WHERE c.taxonomy = 'product_cat';

==========================

Delete alle WooCommerce customers / Users

You Can delete alle WooCommerce customers / users with this plugin :

Bulk Delete