Question

我创建了一个SQL查询来分组，它具有值并按别名排序记录，如下所示：

SELECT * 
FROM   `timeline`, 
       (SELECT Max(mycountview) 
        FROM   (SELECT Count(id_timeline) AS mycountview
                FROM   `timeline` 
                WHERE  type_timeline = '1' 
                GROUP  BY mediaid)AS mycountview)AS max_mycountview
WHERE  type_timeline = '1' 
GROUP  BY mediaid 
HAVING Count(id_timeline) < max_mycountview
ORDER  BY max_mycountview DESC 
LIMIT  0, 5

但我收到了错误：

未知栏＆＃39; max_mycountview＆＃39;在＆＃39;订单条款＆＃39;

如何解决？

Answer 1

您需要将子查询移动到select语句而不是from子句：

SELECT *, 
        (SELECT Max(mycountview) 
        FROM   (SELECT Count(id_timeline) AS mycountview
                FROM   `timeline` 
                WHERE  type_timeline = '1' 
                GROUP  BY mediaid)AS mycountview) AS max_mycountview
FROM   `timeline`
WHERE  type_timeline = '1' 
GROUP  BY mediaid 
HAVING Count(id_timeline) < max_mycountview
ORDER  BY max_mycountview DESC 
LIMIT  0, 5

实际上在重新阅读您的查询后，我不相信这将是最有效的方法。您的查询在表之间执行cross join。但是子查询没有相关性 - 它为每列返回相同的值。在这种情况下，您只需要在子查询中定义列名，以便能够在having和order by子句中访问它：

SELECT * 
FROM   `timeline`,
       (SELECT Max(mycountview) max_mycountview   <!--Define Column Alias Here
        FROM   (SELECT Count(id_timeline) mycountview
                FROM   `timeline` 
                WHERE  type_timeline = '1' 
                GROUP  BY mediaid) t) y
WHERE  type_timeline = '1' 
GROUP  BY mediaid 
HAVING Count(id_timeline) < max_mycountview
ORDER  BY max_mycountview DESC 
LIMIT  0, 5

在MySQL中使用ORDER BY中的别名列

1 个答案: