MySQL查询重写没有子查询可能吗？

Question

是否有可能重写此查询而不使用子查询？

SELECT `products`.`id` AS `id`,`products`.`parent_id` AS `parent_id`,`products`.`lft` AS `lft`,`products`.`rght` AS `rght`,`products`.`primary` AS `primary`,`products`.`friendly` AS `friendly`,`products`.`code` AS `code`,`products`.`title` AS `title`,`products`.`meta_description` AS `meta_description`,`products`.`meta_keywords` AS `meta_keywords`,`products`.`name` AS `name`,`products`.`description` AS `description`,`products`.`purchase_price` AS `purchase_price`,`products`.`sale_price` AS `sale_price`,`products`.`tax_code_id` AS `tax_code_id`,`products`.`colour_id` AS `colour_id`,`products`.`size_id` AS `size_id`,`products`.`num_sales` AS `num_sales`,`products`.`showcase` AS `showcase`,`products`.`showcase_image` AS `showcase_image`,`products`.`classic` AS `classic`,`products`.`new_release` AS `new_release`,`products`.`default_colour_id` AS `default_colour_id`,`products`.`deleted` AS `deleted`,`products`.`stock_level` AS `stock_level`,`products`.`hidden` AS `hidden`,`products`.`manufacturer_id` AS `manufacturer_id`,`products`.`created` AS `created`,`products`.`modified` AS `modified` 
from `products` 
where `products`.`id` NOT IN (
    select `parentproduct`.`id` 
     from `orders` 
      join `baskets` on `orders`.`basket_id` = `baskets`.`id` 
      join `basket_items` on `basket_items`.`basket_id` = `baskets`.`id` AND `basket_items`.`deleted` = 0 
      join `products` on `products`.`id` = `basket_items`.`product_id` 
      left join `products` `parentproduct` on `parentproduct`.`id` = `products`.`parent_id` 
     group by `parentproduct`.`id` 
     having count(*) >= 1 
) 
AND products.parent_id IS NULL AND products.deleted = 0 
ORDER BY name ASC 

我没有想出这个然而，它仍然考虑到产品的孩子没有下令对同一产品的父 - 如果是有道理的？

SELECT parent_products.id, parent_products.name, orders.id 
FROM products 
LEFT JOIN products parent_products ON products.parent_id = parent_products.id 
LEFT JOIN basket_items ON basket_items.product_id = products.id AND basket_items.deleted = 0 
LEFT JOIN baskets ON baskets.id = basket_items.basket_id 
LEFT JOIN orders ON orders.basket_id = baskets.id 
WHERE orders.id IS NULL 
AND products.deleted = 0 
AND parent_products.id IS NOT NULL 
GROUP BY parent_products.name 
ORDER BY parent_products.name ASC 

Answer 1

重写此查询的很好的理由。我会建议将子查询移入视图，然后加入该视图。性能明智的选择将更快。

另外，

SELECT `products`.... 
from `products` 
    left join (
     select `parentproduct`.`id` 
      from `orders` 
       join `baskets` on `orders`.`basket_id` = `baskets`.`id` 
       join `basket_items` on `basket_items`.`basket_id` = `baskets`.`id` AND `basket_items`.`deleted` = 0 
       join `products` on `products`.`id` = `basket_items`.`product_id` 
       left join `products` `parentproduct` on `parentproduct`.`id` = `products`.`parent_id` 
      group by `parentproduct`.`id` 
      having count(*) >= 1 
    ) as Counts 
    ON products.id = Counts.id 
    where Counts.id IS NULL AND products.parent_id IS NULL AND products.deleted = 0 
    ORDER BY name ASC 

它仍然有一个子查询，但现在你有以上的子查询只计算一次，而不是每个产品ID。