Question

我有带有SELECT的SQL UNION (SELECT...)

SELECT virtuemart_product_id 
FROM #__virtuemart_products 
WHERE product_special = 1
UNION
(SELECT virtuemart_product_id
 FROM #__virtuemart_product_badges
 WHERE badge = 3)

此选择将返回47。 12345,54321,...,789,987-例如，最后一个ID来自UNION（#__virtuemart_product_badges）表。

我需要对结果进行排序，以使UNION表中的ID为第一个（union_select_virtuemart_product_id和first_select_virtuemart_product_id之后）。如果我尝试这样做：

...
UNION
    (SELECT virtuemart_product_id
     FROM #__virtuemart_product_badges AS badge
     WHERE badge = 3)
ORDER BY badge.virtuemart_product_id

结果当然是错误的。除ORDER BY以外的任何...ORDER BY virtuemart_product_id都以错误结尾。

这有可能吗？

thx

Answer 1

如果首先要从联合表中获取结果，则在该联合另一个表之后首先选择该表。像这样：-

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Answer 2

您可以尝试一下。它创建一个人工值，该值指示数据来自哪个表，然后按该值在id值之前进行排序。通过更改分配给数据集的值和排序顺序，可以更改首先输出的值：

(SELECT virtuemart_product_id, 0 AS dataset
FROM #__virtuemart_products 
WHERE product_special = 1)
UNION
(SELECT virtuemart_product_id, 1 AS dataset
 FROM #__virtuemart_product_badges
 WHERE badge = 3)
ORDER BY dataset DESC, virtuemart_product_id

修改

由于只需要返回一列（virtuemart_product_id），因此您需要将此查询包装在子查询中，并从中将其SELECT virtuemart_product_id包装起来：

SELECT virtuemart_product_id
FROM ((SELECT virtuemart_product_id, 0 AS dataset
       FROM #__virtuemart_products 
       WHERE product_special = 1)
      UNION
      (SELECT virtuemart_product_id, 1 AS dataset
       FROM #__virtuemart_product_badges
       WHERE badge = 3)
      ORDER BY dataset DESC, virtuemart_product_id) v

Answer 3

尝试仅进行一些嵌套查询：

select * from (YOUR ALL QUERY) AS p order by virtuemart_product_id

MySQL-UNION选择先订购

3 个答案: