MySQL“每个派生表都必须有自己的别名”

我对这种奇怪的行为感到有点困惑。我收到了一个可怕的消息：每个派生表都必须有自己的别名错误

通常，我可以通过在主SELECT语句中添加AS子句来避免这种情况，但是下面的示例不起作用：

SELECT SUM (`a`.`total`) AS `total` FROM (
    SELECT COUNT(DISTINCT(`item_sales`.`id`)) AS `total`,
    (SELECT COUNT(DISTINCT(`sale_item`)) AS `offers` FROM `item_sales_bids` WHERE `user_id` = 2) AS `offers`
        FROM `item_sales`
        INNER JOIN `item_sales_bids` ON `item_sales`.`id` = `item_sales_bids`.`sale_item`
        WHERE `item_sales`.`buyer` != 2
            AND `item_sales`.`sold` = 1
        GROUP BY `item_sales`.`id`
        HAVING `offers` > 0
    ) UNION (
        SELECT COUNT(*) AS `total`,
            `item_sales`.`reserve`,
            (SELECT COUNT(*) FROM `item_sales_bids` WHERE `user_id` = 2) AS `bids`,
            (SELECT MAX(`max_bid`) AS `max` FROM `item_sales_bids` WHERE `user_id` = 2) AS `maxBid`,
            SUM((`item_sales`.`list_date` + (`item_sales`.duration * 86400)) - UNIX_TIMESTAMP()) AS `endTime`
            FROM `item_sales`
            INNER JOIN `item_sales_bids` ON `item_sales_bids`.`sale_item` = `item_sales`.`id`
            GROUP BY `item_sales`.`id`
            HAVING `endTime` < 0
                AND `maxBid` < `item_sales`.`reserve`
    )
) `a`

有人能指出我遗漏了什么吗？请注意，将别名添加到联接会导致相同的错误。

您应该在子查询中放置UNION关键字，如下所示

SELECT SUM (`a`.`total`) AS `total` 
FROM (
    SELECT COUNT(DISTINCT(`item_sales`.`id`)) AS `total`,
    (SELECT COUNT(DISTINCT(`sale_item`)) AS `offers` FROM `item_sales_bids` WHERE `user_id` = 2) AS `offers`
    FROM `item_sales`
    INNER JOIN `item_sales_bids` ON `item_sales`.`id` = `item_sales_bids`.`sale_item`
    WHERE `item_sales`.`buyer` != 2
        AND `item_sales`.`sold` = 1
    GROUP BY `item_sales`.`id`
    HAVING `offers` > 0

UNION 

SELECT COUNT(*) AS `total`,
    `item_sales`.`reserve`,
    (SELECT COUNT(*) FROM `item_sales_bids` WHERE `user_id` = 2) AS `bids`,
    (SELECT MAX(`max_bid`) AS `max` FROM `item_sales_bids` WHERE `user_id` = 2) AS `maxBid`,
    SUM((`item_sales`.`list_date` + (`item_sales`.duration * 86400)) - UNIX_TIMESTAMP()) AS `endTime`
    FROM `item_sales`
    INNER JOIN `item_sales_bids` ON `item_sales_bids`.`sale_item` = `item_sales`.`id`
    GROUP BY `item_sales`.`id`
    HAVING `endTime` < 0
        AND `maxBid` < `item_sales`.`reserve`
) `a`

可以在子查询中包含UNION

SELECT SUM (`a`.`total`) AS `total`
FROM
(
    --- your first query
    UNION
    --- your second query
) a

---

恐怕不行。。。1064-您的SQL语法有错误；请查看与MySQL服务器版本对应的手册，以了解第24行“a”附近使用的正确语法。如果要获取总数，为什么需要在子查询中使用其他内联子查询？