在 SQL MS Access 中添加 Max(Count(column))

Question

我有以下示例数据集，如您所见，X 列是 class ID，Y 列是每个 class 名称，最后 Z 列是其他大学 class 用于每个主题的 ID。目标是通过 X 分组获得 X 和 Z，并获得 Z（其他大学）使用的最常见 ID。

Sheet 1:

X	Y	Z
123	22	122
123	22	123
123	22	122
256	21	256
256	21	255
341	33	400
341	33	400

结果应该是：

X	Z
123	122
256	255
341	400

我尝试添加以下查询，但它只返回所有 table 中的最大值，而不仅仅是 Z 列中的每个值。

SELECT Sheet1.X, Sheet1.Z
  FROM Sheet1
  GROUP BY Sheet1.X, Sheet1.Z
  HAVING COUNT(Sheet1.Z) =
    (SELECT MAX(sheet2.count) FROM
        (SELECT Sheet1.X, Sheet1.Z, COUNT(Sheet1.Z) AS count
        FROM Sheet1
        GROUP BY Sheet1.X, Sheet1.Z) as sheet2);

对我做错了什么有什么建议吗？

Answer 1

这在 MS Access 中是一个真正的痛苦。但是如果你想要每个 X 一个行，那么你可以这样做：

SELECT s1.X, s1.Z
FROM Sheet1 as s1
GROUP BY s1.X, s1.Z
HAVING s1.Z = (SELECT TOP (1) s2.Z
               FROM Sheet1 as s2
               WHERE s2.X = s1.X
               GROUP BY s2.Z
               ORDER BY COUNT(*) DESC, s2.Z
              );

如果您想要在并列的情况下多行，则使用：

SELECT s1.X, s1.Z
FROM Sheet1 as s1
GROUP BY s1.X, s1.Z
HAVING COUNT(*) IN (SELECT TOP (1) COUNT(*)
                    FROM Sheet1 as s2
                    WHERE s2.X = s1.X
                    GROUP BY s2.Z
                   );

我应该注意到，这在任何其他数据库中都会更简单。

在 SQL MS Access 中添加 Max(Count(column))

Add Max(Count(column)) in SQL MS Access

sql

ms-access-2010

ms-access-2016