MYSQL 内连接后过滤结果和 where

Question

我通过内部连接有一个 mysql 查询：

SELECT * FROM oc_product
INNER JOIN oc_product_to_category ON oc_product.product_id = oc_product_to_category.product_id 
WHERE oc_product_to_category.category_id = 100

到目前为止，它返回表 oc_product 中对应于 oc_product_to_category.category_id = 100 的行

我想从这些结果中选择表 oc_product 中的常用行 其中 oc_product_to_category.category_id = 101 或 oc_product_to_category.category_id = 102 等等...

我怎样才能做到这一点？

我尝试通过以下方式：

SELECT * FROM oc_product
INNER JOIN oc_product_to_category ON oc_product.product_id = oc_product_to_category.product_id 
WHERE oc_product_to_category.category_id = 101 OR oc_product_to_category.category_id = 102
having (oc_product_to_category.category_id = 301)

但结果错误。

谁能指出我正确的方向（逻辑）？

Answer 1

您通过通用产品 ID 加入是一回事，这只是直接条件。要包含多个类别，您只需使用“IN”子句并提供您感兴趣的不同类别的列表。

SELECT 
      * 
   FROM 
      oc_product p
         INNER JOIN oc_product_to_category pc
            ON p.product_id = pc.product_id 
            AND pc.category_id IN ( 101, 102, 301 )

现在，您的问题不清楚，但是如果您试图暗示您正在寻找属于 A 类但也与 B 类相关联的产品，并且希望确保这两个类别都被涵盖。以计算机为例。你卖电脑。有人对笔记本电脑（A 类）感兴趣，但也对 i7 处理器（B 类）和 15 英寸屏幕（C 类）感兴趣。您要确保所有 3 个感兴趣的类别都在结果中。您不需要 13 英寸笔记本电脑，也不需要 i7 台式机/塔式机。如果这种情况更多，您可能希望对所需的 3 个类别进行汇总计数。在这种情况下，我会从满足所有 3 个要求的产品/类别表中进行预查询聚合，然后获得符合条件的产品。类似的东西

select
      p.*
   from
      ( select
              -- I only care about the final product ID that qualifies
              pc.product_id
           from
              oc_product_to_category pc
           where
              -- the product category must be of these 3 possible choices
              pc.category_id in ( 101, 102, 301 )
           group by
              pc.product_id
           having
                  -- first SUM() qualifies that the 301 MUST BE included
                  -- hence its = 1 value.
                  sum( case when pc.category_id = 301 
                            then 1 else 0 end ) = 1
              AND 
                  -- AND the sum() of the others is GREATER than 0.
                  -- so either OR both would qualify the product
                  sum( case when pc.category_id in ( 101, 102 )
                            then 1 else 0 end ) > 0  ) JustQualified
         -- NOW, joining to the products based on only those that qualified above
         JOIN oc_product p
            on JustQualified.product_id = p.product_id

相关更新

要对上述查询中我作为别名“p”的 OC_Product 表执行相关更新查询，只需对语法稍作更改

update oc_product p
   JOIN ( select
                  -- I only care about the final product ID that qualifies
                  pc.product_id
               from
                  oc_product_to_category pc
               where
                  -- the product category must be of these 3 possible choices
                  pc.category_id in ( 101, 102, 301 )
               group by
                  pc.product_id
               having
                      -- first SUM() qualifies that the 301 MUST BE included
                      -- hence its = 1 value.
                      sum( case when pc.category_id = 301 
                                then 1 else 0 end ) = 1
                  AND 
                      -- AND the sum() of the others is GREATER than 0.
                      -- so either OR both would qualify the product
                      sum( case when pc.category_id in ( 101, 102 )
                                then 1 else 0 end ) > 0  ) JustQualified
             -- NOW, joining to the products based on only those that qualified above
      on JustQualified.product_id = p.product_id
   set p.myColumn = 22