Question

我正在尝试在Microsoft Access中编写一个前n值查询，其中n可能会按组更改。例如，一组可能是前3条记录，另一组可能是前2条记录，另一组可能是前4条记录。我有一个表格，其中包含“TopN”字段，其中我存储了为该组显示的值的数量。

前3个查询的示例有效，我试图用Top N替换Top 3，其中N是DLookup或使用TopN字段中的值的东西：

SELECT Payout.GDate, Payout.[Game Type], Payout.Denom, Payout.Segment, Payout.Manufacturer_Description, Payout.Stand, Payout.Payout
  FROM Payout, PayoutShowSegment
  WHERE (((Payout.Payout) IN (SELECT TOP 3 [Payout] 
                                FROM [Payout] 
                                WHERE [Payout].[Segment]=[PayoutShowSegment].[Segment])))
  ORDER BY Payout.[Game Type], Payout.Denom, Payout.Payout DESC;

Answer 1

几个月前我遇到过类似的问题。

使用您的查询，这样的事情应该有效：

SELECT      T1.GDate, 
            T1.[Game Type], 
            T1.Denom, 
            T1.Segment, 
            T1.Manufacturer_Description, 
            T1.Stand, 
            T1.Payout
FROM        Payout T1 INNER JOIN Payout T2 ON
                T1.[Game Type] = T2.[Game Type] AND
                T1.Denom = T2.Denom AND
                T1.Segment = T2.Segment AND
                T1.Manufacturer_Description = T2.Manufacturer_Description AND
                T1.Stand = T2.Stand AND
                T1.Payout = T2.Payout AND
                T1.GDate >= T2.GDate
GROUP BY    T1.GDate, 
            T1.[Game Type], 
            T1.Denom, 
            T1.Segment, 
            T1.Manufacturer_Description, 
            T1.Stand, 
            T1.Payout
HAVING      COUNT(*) <= (
                         SELECT TopN
                         FROM   MyOtherTable
                         WHERE  MyOtherTable.IDField = T1.IDField
                        )
ORDER BY    T1.GDate

注意 - 联接可能会缩减为Payout表中的PK。

有关详情，请查看此网站：http://www.sql-ex.com/help/select16.php

访问前N个查询，其中N按组更改

1 个答案: