Question

我有一个Access报告，该报告的Record Source引用了表单上的几个字段。工作正常。就是这样，为简单起见，在SELECT子句中减去了一堆字段：

SELECT
    pt.PA,
    pt.SpfCode
FROM
    PtHead AS pt
    LEFT JOIN tblProblems AS p ON pt.PA = p.PantagNo
WHERE
    pt.PA = [Forms]![fdlgQualityHistory]![PA] AND
    p.ComplaintDate >= [Forms]![fdlgQualityHistory]![StartDate];

我想升级此报告，使其仅显示最新记录。效果很好：

SELECT TOP 20  -- NEW PART
    pt.PA,
    pt.SpfCode
FROM
    PtHead AS pt
    LEFT JOIN tblProblems AS p ON pt.PA = p.PantagNo
WHERE
    pt.PA = [Forms]![fdlgQualityHistory]![PA] AND
    p.ComplaintDate >= [Forms]![fdlgQualityHistory]![StartDate]
ORDER BY p.ComplaintDate DESC;  -- NEW PART

但是，我不希望将其硬编码为TOP 20。我希望它是TOP x，基于相同表单上的另一个字段。以下失败：

SELECT TOP [Forms]![fdlgQualityHistory]![MaxProblems]  -- FAILS HERE
    pt.PA,
    pt.SpfCode
FROM
    PtHead AS pt
    LEFT JOIN tblProblems AS p ON pt.PA = p.PantagNo
WHERE
    pt.PA = [Forms]![fdlgQualityHistory]![PA] AND
    p.ComplaintDate >= [Forms]![fdlgQualityHistory]![StartDate]
ORDER BY p.ComplaintDate DESC;

错误：

SELECT语句包含的保留字或参数名称拼写错误或丢失，或者标点符号不正确。

我可以更改语法以使其工作吗？如果没有，我该怎么办？每次通过VBA运行报告时，是否都必须覆盖整个查询文本？

Answer 1

Access does not support using a parameter for SELECT TOP.

在该[Forms]![fdlgQualityHistory]![MaxProblems]控件的更新后事件中修订记录源 SQL。

Answer 2

或者，由于无法TOP数字进行参数化，因此无法使用表单字段，因此请考虑通过递减日期来创建运行计数，然后可以对其进行过滤。但是请注意，对于较大的表，此相关子查询可能会带来性能挑战。

SELECT 
    pt.PA,
    pt.SpfCode
FROM
    PtHead AS pt
    LEFT JOIN tblProblems AS p ON pt.PA = p.PantagNo
WHERE
     pt.PA = [Forms]![fdlgQualityHistory]![PA]
 AND p.ComplaintDate >= [Forms]![fdlgQualityHistory]![StartDate]
 AND (SELECT Count(*) 
      FROM PtHead sub_pt
      LEFT JOIN tblProblems AS sub_p ON sub_pt.PA = sub_p.PantagNo
      WHERE sub_p.ComplaintDate >= p.ComplaintDate) <= [Forms]![fdlgQualityHistory]![MaxProblems];

也许有一天，MS Access将支持窗口功能，并在RDBMS世界中加入其他功能，以避免相关的子查询：

ROW_NUMBER() OVER (ORDER BY pt.ComplaintDate DESC)

在MS Access查询中基于表单字段的SELECT TOP x？

2 个答案: