为什么此 SQL 查询返回错误？答案

【问题标题】：Why does this SQL Query returns an error?为什么此 SQL 查询返回错误？
【发布时间】：2014-01-26 07:31:42
【问题描述】：

我正在使用子查询来访问 where 子句中的别名。只要我只选择“MIN（r.price）”，它就可以正常工作。当我选择“*, ...”时，它会返回错误“...duplicate column id ...”。这是为什么？子查询本身运行良好。

这里是：

SELECT *
FROM
(
    SELECT *, MIN(r.price) as min_price
    FROM tl_frp_presentation as p
    INNER JOIN tl_frp_object as o
        ON p.objectID = o.id
    INNER JOIN tl_tag as c
        ON c.id = o.id
        AND c.from_table = "tl_frp_object"
    LEFT JOIN tl_frp_rooms as r
        ON r.pid = o.id
    WHERE p.type = "tl_frp_object"
    GROUP BY p.id
) as inner_t
WHERE min_price >= 100

感谢任何帮助！

【问题讨论】：

标签： mysql sql select group-by having

【解决方案1】：

只需将 ALIAS 名称添加到列

试试这个：

SELECT *
FROM (SELECT *, MIN(r.price) AS min_price 
      FROM tl_frp_presentation AS p
      INNER JOIN tl_frp_object AS o ON p.objectID = o.id
      INNER JOIN tl_tag AS c ON c.id = o.id AND c.from_table = "tl_frp_object"
      LEFT JOIN tl_frp_rooms AS r ON r.pid = o.id
      WHERE p.type = "tl_frp_object"
      GROUP BY p.id
     ) AS inner_t
WHERE min_price >= 100;

您也可以使用 HAVING 子句来满足您的要求，如下所示

SELECT *, MIN(r.price) AS min_price 
FROM tl_frp_presentation AS p
INNER JOIN tl_frp_object AS o ON p.objectID = o.id
INNER JOIN tl_tag AS c ON c.id = o.id AND c.from_table = "tl_frp_object"
LEFT JOIN tl_frp_rooms AS r ON r.pid = o.id 
WHERE p.type = "tl_frp_object"
GROUP BY p.id HAVING min_price >= 100;

【讨论】：

谢谢！你的第二个代码太棒了..还不知道 HAVING 关键字。
@Yami 而不是使用SELECT *，只通过在查询的 SELECT 部分传递列名来获取特定的行
我没有，因为在当前情况下我确实需要所有列。但感谢您的意见。

【解决方案2】：

你给子选择一个别名，这很好！

使用它:-)

) as inner_t
WHERE inner_t.min_price >= 100

更好的是，您不需要将其包装到子选择中：

SELECT *, MIN(r.price) as min_price
FROM tl_frp_presentation as p
INNER JOIN tl_frp_object as o
    ON p.objectID = o.id
INNER JOIN tl_tag as c
    ON c.id = o.id
    AND c.from_table = "tl_frp_object"
LEFT JOIN tl_frp_rooms as r
    ON r.pid = o.id
WHERE p.type = "tl_frp_object"
GROUP BY p.id
HAVING min_price >= 100

【讨论】：