如何在SQL的WHERE子句中將AND運算符與AND運算符一起使用？

Question

我在CodeIgniter模型中使用此數據庫查詢。

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)

它返回我：

我只需要那些滿足sub_category_value_id所有條件的產品。 現在，它返回所有條件。

我是數據庫新手，對查詢了解不多。

Answer 1

似乎您不應該對product_category表使用左連接。 LEFT JOIN關鍵字返回左表中的所有記錄（ product_category ），請嘗試如下操作：

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

您想要group by並having 。 您不清楚“所有條件”是什么意思，但是看起來像這樣：

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;

筆記：

• WHERE子句將LEFT JOIN轉換為INNER JOIN ，因此請使用正確的JOIN 。
• 我假設您要從子類別表中獲取一對值。
• HAVING子句堅持兩個子類別都匹配。

Answer 3

下面的查詢將根據給定的vendor_id，category_id，subcategory_id和subcategory_value_id為您提供具有product_id和product_name的不同產品。

讓我知道這是否適合您！

SELECT 
DISTINCT p.product_id,
p.product_name 
FROM products AS p
LEFT JOIN product_category AS pc ON p.product_id = pc.product_id
LEFT JOIN vendor_products AS vp ON p.product_id = vp.product_id
LEFT JOIN subcategories AS sc ON sc.subcategory_id = pc.subcategory_id
LEFT JOIN subcategories_value AS scv ON scv.subcategory_value_id = pc.subcategory_value_id
WHERE vp.vendor_id = 2 
    AND vp.category_id = 2 
    AND pc.subcategory_id IN (1, 2) 
    AND scv.subcategory_value_id IN (1, 4)
ORDER BY p.product_id;