如何在SQL的WHERE子句中将AND运算符与AND运算符一起使用？

Question

我正在CodeIgniter模型中使用此数据库查询。

SELECT
                p.product_id,
                p.product_name,
                p.product_photo,
                p.size,
                p.price,
                p.status,
                p.product_image_path
            FROM
                products AS p
            LEFT JOIN
                product_category AS pc
            ON
                p.product_id = pc.product_id
            LEFT JOIN
                vendor_products AS vp
            ON
                vp.product_id = pc.product_id
            WHERE
                pc.category_id = 2
            AND
                vp.vendor_id = 36
            AND 
                pc.subcategory_id IN (1,2)
            AND
                pc.subcategory_value_id IN (1,4)

它返回了我：

我只希望那些满足sub_category_value_id所有条件的产品。现在，它返回所有条件。

我是数据库新手，对查询了解不多。

Answer 1

似乎您不应该对product_category表使用左联接。 LEFT JOIN关键字返回左表（product_category）中的所有记录，请尝试如下操作：

SELECT
                p.product_id,
                p.product_name,
                p.product_photo,
                p.size,
                p.price,
                p.status,
                p.product_image_path
            FROM
                products AS p
            INNER JOIN
                product_category AS pc
            ON
                p.product_id = pc.product_id
            LEFT JOIN
                vendor_products AS vp
            ON
                vp.product_id = pc.product_id
            WHERE
                pc.category_id = 2
            AND
                vp.vendor_id = 36
            AND 
                pc.subcategory_id IN (1,2)
            AND
                pc.subcategory_value_id IN (1,4)

Answer 2

您需要group by和having。您不清楚“所有条件”是什么意思，但是看起来像这样：

SELECT p.*
FROM products p JOIN
     product_category pc
     ON p.product_id = pc.product_id JOIN
     vendor_products AS vp
     ON vp.product_id = pc.product_id
WHERE pc.category_id = 2 AND
      vp.vendor_id = 36 AND
      (pc.subcategory_id, pc.subcategory_value_id) IN ( (1, 1), (2, 4) )
GROUP BY p.product_id  -- this is okay because it is presumably the primary key
HAVING COUNT(DISTINCT pc.subcategory_id) = 2;

注意：

• WHERE子句将LEFT JOIN变成INNER JOIN，因此请使用正确的JOIN。
• 我假设您要从子类别表中获取一对值。
• HAVING子句坚持两个子类别都匹配。

Answer 3

以下查询将根据给定的vendor_id，category_id，subcategory_id和subcategory_value_id为您提供具有product_id和product_name的不同产品。

让我知道这是否适合您！

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