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我有一个 sql 查询，由于链接产品的产品 id 重复，返回了一些不正确的结果，所以我在查询的末尾添加了以下内容，希望它只采用任何产品 id 的第一个实例：

AND pc.products_id 
IN
(SELECT
pc.products_id, MIN(categories_id)
FROM
zen_products_to_categories pc
GROUP BY
pc.products_id)

但是当我运行该过程时，我得到一个 Operand should contain 1 column(s) 错误。我自己运行了该查询，它只给了我每个产品 ID 一次，所以不知道为什么我会收到错误。

我现在的完整查询是：

SELECT p.products_quantity, p.abebooks_status, 
p.products_id AS id, 
p.products_status AS prodStatus, 
FORMAT( IFNULL(s.specials_new_products_price, p.products_price),2) AS price, 
pc.categories_id AS prodCatID, 
c.parent_id AS catParentID, 
cd.categories_name AS catName 
FROM 
zen_products p 
JOIN zen_products_description pd ON p.products_id=pd.products_id 
JOIN zen_products_to_categories pc ON p.products_id=pc.products_id 
JOIN zen_categories c ON pc.categories_id=c.categories_id 
JOIN zen_categories_description cd ON c.categories_id=cd.categories_id 
left join zen_specials s on ( s.products_id = p.products_id AND ( (s.expires_date > CURRENT_DATE) OR (s.expires_date = 0) ) ) 
WHERE p.products_price > 0 and p.products_status = 1 
AND pc.products_id 
IN 
(SELECT pc.products_id, MIN(categories_id) 
FROM zen_products_to_categories pc GROUP BY pc.products_id) 
ORDER BY catName ASC

谁能告诉我为什么当我添加额外的查询时它不起作用，因为它让我感到困惑

4

2 回答 2

1

您可以尝试：

AND (pc.products_id, pc.categories_id) 
    IN
    (SELECT
       pc.products_id, MIN(categories_id)
     FROM
       zen_products_to_categories pc
     GROUP BY
       pc.products_id)

编辑：

在 MySQL 中，这样的子查询通常很慢。JOIN 应该会带来更好的运气：

SELECT ....
FROM
  ....
  INNER JOIN (SELECT
                products_id, MIN(categories_id) min_categories_id
              FROM
                zen_products_to_categories
              GROUP BY
                products_id) min_ct
  ON pc.products_id=min_ct.products_id
     AND pc.categories_id=min_ct.min_categories_id
WHERE
  ....
于 2013-11-28T07:45:29.317 回答
0

MIN(categories_id)当您匹配从子查询中删除的单列时，子查询应返回一列

AND pc.products_id 
IN
(SELECT
pc.products_id
FROM
zen_products_to_categories pc
GROUP BY
pc.products_id)
于 2013-11-28T07:45:34.477 回答