Question

我有一个报告跟踪某些项目在数据库中的持续时间，并通过一系列年龄范围（20-44,45-60,61-90,91-180,180 +）跟踪它）。我有以下查询作为报告的数据源：

SELECT DISTINCT Source.ItemName, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) > 20) AS Total, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) BETWEEN 20 AND 44) AS BTWN_20_44, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) BETWEEN 45 AND 60) AS BTWN_45_60, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) BETWEEN 61 AND 90) AS BTWN_61_90, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) BETWEEN 91 AND 180) AS BTWN_91_180, 
Count(SELECT Source.DateAdded FROM Source WHERE Int(Date()-Source.DateAdded) > 180) AS GT_180
FROM Source
GROUP BY Source.ItemName;

此查询效果很好，除非列中没有任何条目。而不是返回0的计数，返回一个空值。

如何让Count（）返回0而不是空？

Answer 1

您可以返回

ISNULL(Count(......), 0)

一切都应该没问题 - 将在MS SQL Server中 - 但我刚看到你正在使用Access。由于我不太了解Access，我不确定这会起作用 - 你可以试试吗？

好的 - 很高兴看到Access中有类似的内容（如果与SQL Server中的内容完全不同）。

马克

Answer 2

更好的是，使用Nz()例如

Nz(Count(SELECT Source.DateAdded 
            FROM Source 
            WHERE Int(Date()-Source.DateAdded), 0)

当结果为null时返回0，否则返回。

请注意Nz()函数是Access对象模型的一部分，因此仅在Access用户界面中使用时才可用。如果您使用没有Access UI的Access数据库引擎（通过OLE DB，ODBC等从另一个应用程序），那么您将收到错误，“表达式中未定义的函数'Nz'。”

Answer 3

第二个虽然（没有更多信息）我认为你这个查询非常错误....

正如我所说，当我尝试原始查询时，我收到错误“此子查询最多可以返回一条记录”。

这可能更接近你想要的东西

SELECT DISTINCT Source.ItemName, 
    (SELECT count(Source.DateAdded ) FROM Source 
        WHERE Int(Date()-Source.DateAdded)> 20)  AS Total, 
    (SELECT count(Source.DateAdded ) FROM Source  
        WHERE Int(Date()-Source.DateAdded) BETWEEN 20 AND 44) AS BTWN_20_44, 
    (SELECT count(Source.DateAdded ) FROM Source  
        WHERE Int(Date()-Source.DateAdded) BETWEEN 45 AND 60) AS BTWN_45_60, 
    (SELECT count(Source.DateAdded ) FROM Source  
        WHERE Int(Date()-Source.DateAdded) BETWEEN 61 AND 90) AS BTWN_61_90, 
    (SELECT count(Source.DateAdded ) FROM Source  
        WHERE Int(Date()-Source.DateAdded) BETWEEN 91 AND 180) AS BTWN_91_180, 
    (SELECT count(Source.DateAdded ) FROM Source  
        WHERE Int(Date()-Source.DateAdded) > 180) AS GT_180
FROM Source
GROUP BY Source.ItemName;

除非你试图计算每个项目名称的数量......在这种情况下，它有点棘手。

Answer 4

将Count语句替换为

Sum(Iif(DateDiff("d",DateAdded,Date())>=91,Iif(DateDiff("d",DateAdded,Date())<=180,'1','0'),'0')) AS BTWN_91_180,

我不是嵌套Iif的粉丝，但看起来并没有任何方法，因为DateDiff和BETWEEN...AND的播放效果不佳。< / p>

要修剪ItemName s而不添加任何日期，查询块必须包含在更大的查询中，因为无法从查询内部对计算字段进行检查。最终结果是这个查询：

SELECT *
FROM 
     (
     SELECT DISTINCT Source.ItemName AS InvestmentManager, 
     Sum(Iif(DateDiff("d",DateAdded,Date())>=20,Iif(DateDiff("d",DateAdded,Date())<=44,'1','0'),'0')) AS BTWN_20_44,
     Sum(Iif(DateDiff("d",DateAdded,Date())>=45,Iif(DateDiff("d",DateAdded,Date())<=60,'1','0'),'0')) AS BTWN_45_60,
     Sum(Iif(DateDiff("d",DateAdded,Date())>=61,Iif(DateDiff("d",DateAdded,Date())<=90,'1','0'),'0')) AS BTWN_61_90,
     Sum(Iif(DateDiff("d",DateAdded,Date())>=91,Iif(DateDiff("d",DateAdded,Date())<=180,'1','0'),'0')) AS BTWN_91_180,
     Sum(Iif(DateDiff("d",DateAdded,Date())>180,'1','0')) AS GT_180,
     Sum(Iif(DateDiff("d",DateAdded,Date())>=20,'1','0')) AS Total
     FROM Source
     WHERE CompleteState='FAILED'
     GROUP BY ItemName
     )
WHERE Total > 0;

创建一个查询Count（）返回0而不是空

4 个答案: