SELECT categories.category_id, categories.title, categories.description,categories.parent_id,categories.display_weight,
categories.image_thumb, categories.deleted, categories.image_banner,
FROM categories 
WHERE 
AND parent_id=18
AND category_id <> 18

SELECT `product.product_id`, `product.name`, `product.image_thumb`, `product.deleted` 
FROM (`product`) 
WHERE `product_id` IN (select product_id from product_category where category_id=18) 
ORDER BY `display_weight` DESC

SELECT p.product_id, p.name, p.image_thumb, p.deleted ,
c.category_id, c.title, c.description,c.parent_id,c.display_weight,
c.image_thumb, c.deleted, c.image_banner
FROM product p
JOIN product_category pc
ON pc.product_id = p.product_id 
LEFT JOIN categories c
ON c.parent_id = ps.category_id
AND c.category_id <> ps.category_id
ORDER BY p.display_weight DESC