Question

我试图为每个没有接受答案的StackOverflow问题获得最高投票答案的平均分数。

使用以下查询：

SELECT AVG(MaxScore) 
FROM
    (SELECT MAX(a.Score) as MaxScore
     FROM Posts a
     JOIN Posts q ON q.Id = a.ParentID
     WHERE q.PostTypeId = 1 AND q.AcceptedAnswerId IS NULL
     GROUP BY q.Id);

只给了我：＆＃34;＆＃39;＆＃39;＆＃39;＆＃34;

附近的语法不正确

任何想法为什么？谢谢！

Answer 1

SELECT AVG(MaxScore) 
FROM
    (SELECT MAX(a.Score) as MaxScore
     FROM Posts a
     JOIN Posts q ON q.Id = a.ParentID
     WHERE q.PostTypeId = 1 AND q.AcceptedAnswerId IS NULL
     GROUP BY q.Id) AS sub;

可能需要这样的子查询的名称，具体取决于数据库系统，即使您不使用它。

max - SQL的平均值

1 个答案: