Question

我有这样的查询：

SELECT pov.product_id
 ,  (SELECT AVG(r1.rating) AS total 
       FROM oc_review r1 
      WHERE r1.product_id = pov.product_id 
        AND r1.status = 1 
      GROUP 
         BY r1.product_id) AS rating
 ,  (SELECT price 
       FROM oc_product_special ps 
      WHERE ps.product_id = pov.product_id 
        AND ps.customer_group_id = 1
        AND (
              (ps.date_start = '0000-00-00' OR ps.date_start < NOW()) 
          AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW())
            ) 
        ORDER 
           BY ps.priority ASC
          ,  ps.price ASC 
      LIMIT 1
    ) AS special 
 FROM oc_product_option_value pov 
 LEFT 
 JOIN oc_product_to_category p2c 
   ON pov.product_id = p2c.product_id
 LEFT 
 JOIN oc_product p 
   ON p.product_id = pov.product_id 
 LEFT 
 JOIN oc_product_special ps 
   ON ps.product_id = pov.product_id
WHERE p2c.category_id = 62 
  AND pov.option_id = 13 
  AND pov.quantity > 0 
ORDER 
   BY p.date_added DESC 
LIMIT 54

如果我不使用LIMIT，则我的查询有200多个结果，但是当我限制54个结果时，我的查询有21个结果。为什么？在验证表中的条件而不是第一选择的总和后，我该如何限制结果？

Answer 1

这是Opencart数据库。您的尝试有多个问题。

product_option_value将为option_value_id具有多个product_id值。您需要使用Distinct才能获得独特的产品。
您无需在oc_product上进行左联接，因为如果没有product_option_value_id表中的product_id，那么oc_product就不会存在。
由于您正在category_id上进行搜索，因此您也可以将left join表上的oc_product_to_category更改为inner join。

尝试：

SELECT DISTINCT pov.product_id
 ,  (SELECT AVG(r1.rating) AS total 
       FROM oc_review r1 
      WHERE r1.product_id = pov.product_id 
        AND r1.status = 1 
      GROUP 
         BY r1.product_id) AS rating
 ,  (SELECT price 
       FROM oc_product_special ps 
      WHERE ps.product_id = pov.product_id 
        AND ps.customer_group_id = 1
        AND (
              (ps.date_start = '0000-00-00' OR ps.date_start < NOW()) 
          AND (ps.date_end = '0000-00-00' OR ps.date_end > NOW())
            ) 
        ORDER 
           BY ps.priority ASC
          ,  ps.price ASC 
      LIMIT 1
    ) AS special 
 FROM oc_product_option_value pov 
 INNER 
 JOIN oc_product_to_category p2c 
   ON pov.product_id = p2c.product_id
 INNER  
 JOIN oc_product p 
   ON p.product_id = pov.product_id 
 LEFT 
 JOIN oc_product_special ps 
   ON ps.product_id = pov.product_id
WHERE p2c.category_id = 62 
  AND pov.option_id = 13 
  AND pov.quantity > 0 
ORDER 
   BY p.date_added DESC 
LIMIT 54

MySQL限制子查询不是主体查询

1 个答案: