Question

我正在尝试运行此查询：

SELECT
    gc_category_products.product_id, 
    LEAST(IFNULL(NULLIF(saleprice, 0), price),price) AS sort_price,
    GROUP_CONCAT(CONVERT(category_id, CHAR(8))) AS cats
FROM
    (`gc_category_products`)
JOIN `gc_products` ON `gc_category_products`.`product_id` = `gc_products`.`id`
WHERE
        `category_id` = '31'
    OR `category_id` = '35'
    OR `category_id` = '30'
    OR `category_id` = '36'
    OR `category_id` = '37'
    OR `category_id` = '34'
AND 
    `enabled` = 1
GROUP BY
    `product_id`
LIMIT 10

在cats字段中，它只返回一个数字，如果我取出所有WHERE子句，它会带回一个以逗号分隔的列表，但我需要那些WHERE来过滤我的数据。

有什么想法吗？

示例数据

gc_category_products
--------------------------
product_id | category_id |
--------------------------
3          | 31          |
3          | 18          |
4          | 35          |
4          | 21          |


gc_products
-----------------------------------
| id | price | saleprice | enabled|
-----------------------------------
| 3  | 23.00 | 0.00      | 1      |
| 4  | 50.00 | 0.00      | 1      |

expected result
--------------------------------
product_id | sort_price | cats |
--------------------------------
| 3        | 23.00      | 31,18|
| 4        | 50.00      | 35,21|

Answer 1

对我而言，这听起来像你想要的，你想要某些类别的产品，包括他们所在的所有类别的列表; < / p>

SELECT
    cat.product_id, 
    LEAST(IFNULL(NULLIF(saleprice, 0), price),price) AS sort_price,
    GROUP_CONCAT(category_id) AS cats
FROM gc_category_products cat
JOIN gc_products p ON cat.product_id = p.id
WHERE cat.product_id IN
  (SELECT product_id 
   FROM gc_category_products gcp 
   WHERE gcp.category_id IN ('31','35','30','36','37','34'))
AND enabled=1
GROUP BY product_id

PRODUCT_ID   SORT_PRICE   CATS
3            23           31,18
4            50           35,21

SQLfiddle for testing

Answer 2

WHERE子句会过滤掉您在结果集中预期的其他category_id：'18'和'21'。此查询生成所需的结果集：

SELECT
    gc_category_products.product_id, 
    LEAST(IFNULL(NULLIF(saleprice, 0), price),price) AS sort_price,
    GROUP_CONCAT(CONVERT(category_id, CHAR(8))) AS cats
FROM
    (`gc_category_products`)
JOIN `gc_products` ON `gc_category_products`.`product_id` = `gc_products`.`id`
WHERE
       `category_id` = '31'
    OR `category_id` = '35'
    OR `category_id` = '30'
    OR `category_id` = '36'
    OR `category_id` = '37'
    OR `category_id` = '34'
    OR `category_id` = '18' /* added */
    OR `category_id` = '21' /* added */
AND 
    `enabled` = 1
GROUP BY
    `product_id`
LIMIT 10

可以在此处找到生成预期结果集的测试示例：http://sqlfiddle.com/#!2/71a20/17

但，请注意您的查询还有其他潜在问题。

The OR logical operator has lower precedence than AND。因此，您的查询可能无法达到预期效果。
如果Joachim has correctly interpreted your intent，您应该修改WHERE子句以包含执行过滤的子查询。以这种方式构建查询可确保不从最终结果集中过滤其他类别。

WHERE enabled = 1 和EXISTS（选择1 从gc_category_products起x 在x。product_id = gc_products。id 和x。category_id IN （ '31'， '35'， '30'， '36'， '37'， '34'））

此附加修改已经过测试，符合您的规范：http://sqlfiddle.com/#!2/71a20/21/0

试图获取逗号分隔列表但只获得一个

2 个答案: