搜索一个

Question

我有以下表格：

表格：属性

+---------------+-------------+
| attribute_id  | name        |
+---------------+-------------+
| 1             | color       |
| 2             | material    |
+---------------+-------------+

表格： attribute_values

+---------------------+-----------------+--------------+--------------+
| attribute_value_id  | attribute_id    | product_id   | value        |
+---------------------+-----------------+--------------+--------------+
| 1                   | 1               | 1            | blue         |
| 2                   | 2               | 1            | metal        |
| 3                   | 1               | 2            | red          |
| 4                   | 2               | 2            | metal        |
+---------------------+-----------------+--------------+--------------+

我有以下问题：

    SELECT
                p.product_id                AS product_id,
                p.name                      AS product_name,
                v.value                     AS attribute_value,
                a.attribute_id              AS attribute_id,
                a.attribute_category_id     AS attribute_category_id,
                a.name                      AS attribute_name,
                c.name                      AS attributes_category_name
    FROM
                products p
    LEFT JOIN
                attribute_values v USING (product_id)
    LEFT JOIN
                attributes a USING (attribute_id)
    LEFT JOIN
                attribute_categories c USING (attribute_category_id)
    WHERE
                (a.name = 'color' AND v.value = 'red')

查询的问题是：当产品与WHERE-clausule匹配时，我需要所有属性。

所以，我得到的原因是：我只获得了颜色＆＃39; -attribute，但正如您所看到的，特定产品还有一个＆＃39;材料＆ ＃39; -attibute

因此，当我搜索红色的产品时，我也想要特定产品的OTHER属性（材料=金属）。

Answer 1

这是一个想法 - 简化为其本质......

SELECT x.* 
  FROM 
     ( SELECT product_id
            , MAX(CASE WHEN attribute_id = 1 THEN value END) color
            , MAX(CASE WHEN attribute_id = 2 THEN value END) material 
         FROM attribute_values 
        GROUP 
           BY product_id
     ) x
 WHERE color = 'red';

哦，请注意，attribute_value_id似乎没有用处。

Answer 2

我想我找到了答案：

    SELECT
                p.product_id                AS product_id,
                p.name                      AS product_name,
                v.value                     AS attribute_value,
                a.attribute_id              AS attribute_id,
                a.attribute_category_id     AS attribute_category_id,
                a.name                      AS attribute_name,
                c.name                      AS attributes_category_name
    FROM
                products p
    LEFT JOIN
                attribute_values v USING (product_id)
    LEFT JOIN
                attributes a USING (attribute_id)
    LEFT JOIN
                attribute_categories c USING (attribute_category_id)
    WHERE
                p.product_id IN (SELECT p.product_id FROM products p LEFT JOIN attribute_values v USING (product_id) LEFT JOIN attributes a USING (attribute_id) WHERE a.name = 'color' AND v.value = 'red')