sqldf 仅返回一行，与 SQL 中使用的查询相同

Question

出于某种原因，当涉及到 R 时，我只返回一行，而在 SQL 服务器上，我返回正确的行数。 SQL东风：

CustomerCodingChangesT <- sqldf("
        SELECT c.CustID as ID 
             , c.ReverseSupplier as Supplier
             , c.ReverseCustomerCode as Code
             , c.Name
             , c.Address
             , c.[From PostCode]
             , c.[From Outlet]
             , c.[From OutletName] 
             , o.FullAddress AS [From Address]
             , c.[To PostCode]
             , c.[To Outlet]
             , c.[To OutletName]
             , o1.FullAddress AS [To Address]
             , MAX(CAST(c.TotalUnits AS VARCHAR)) AS [Total Units]
             , '$'+MAX(CAST(c.TotalValue AS VARCHAR)) AS [Total Value]
             , '' AS Checked
             , c.CustRecActive as Active

        FROM CustomerCorrectionSummaryT AS c
        LEFT JOIN OutletMasterT AS o 
             ON  c.[From PostCode] = o.Postcode 
             AND c.[From Outlet] = o.Outlet 
        LEFT JOIN OutletMasterT AS o1 
             ON  c.[To PostCode] = o1.Postcode 
             AND c.[To Outlet] = o1.Outlet
        ORDER BY c.totalvalue DESC;")

SQL:

if object_id ('tempdb..#CustomerCodingChanges') is not null drop table #CustomerCodingChanges

SELECT c.CustID as ID
     , c.ReverseSupplier as Supplier
     , c.ReverseCustomerCode as Code
     , c.Name
     , c.Address
     , c.[From Postcode]
     , c.[From Outlet]
     , c.[From OutletName]
     , o.FullAddress AS [From Address]
     , c.[To Postcode]
     , c.[To Outlet]
     , c.[To OutletName]
     , o1.FullAddress AS [To Address]
     , CAST(c.TotalUnits AS VARCHAR(MAX)) AS [Total Units]
     , '$'+CAST(c.TotalValue AS VARCHAR(MAX)) AS [Total Value]
     , '' AS Checked 
     , c.CustRecActive as Active

INTO #CustomerCodingChanges
FROM #CustomerCorrectionSummary AS c
LEFT JOIN ndf_061.IRGMaster.dbo.OutletMaster AS o 
     ON  c.[From Postcode] = o.postcode 
     AND c.[From Outlet] = o.outlet
LEFT JOIN ndf_061.IRGMaster.dbo.OutletMaster AS o1 
     ON  c.[To Postcode] = o1.postcode 
     AND c.[To Outlet] = o1.outlet
ORDER BY c.totalvalue DESC;

CustomerCorrectionSummaryT 和 OutletMasterT 的数据帧在 R 和 SQL Server 中的结果数量相同，所以我不知道为什么它不会显示相同的结果R 与 SQL 服务器中的结果数。在 SQL 服务器查询中 returns 22 行，而在 R 中我只得到一行都是正确的。 R 的 sqldf 只是没有显示所有内容。我认为这与我的 left join 功能有关，但我真的不知道。如果您需要更多信息，请告诉我！

Answer 1

如果你仔细查看，这两个查询是不一样的。值得注意的是，您在第一个查询 MAX 中调用了一个聚合，而您在第二个查询中没有调用该聚合。因此，第一个查询是一个聚合查询，它通过返回聚合的各种分组折叠单元级行（SUM、COUNT、AVG、MIN、MAX、等）在指定列上。

此外，因为您没有包含 GROUP BY 子句，在标准 ANSI SQL 中，第一个查询应该会引发错误。不幸的是，对于 SQL 的新手来说，一些方言如 SQLite 和 MySQL 允许这样的语法。而R的sqldf 运行s SQLite默认。事实上，如果你运行在 SQL 服务器中的第一个查询，它会出错，因为你运行一个不正确的聚合查询 GROUP BY 子句中没有包含非聚合列尽管它们在 SELECT 子句中指定。

仔细观察，您似乎试图在 SQL Server

中翻译以下表达式

CAST(c.TotalUnits AS VARCHAR(MAX)) AS [Total Units]

这与第一个查询中尝试的行不同：

MAX(CAST(c.TotalUnits AS VARCHAR)) AS [Total Units]

SQLite实际上不维护maximum length in VARCHAR 类型。因此，只需保留原始行而无需聚合或大小限制：

CAST(c.TotalUnits AS VARCHAR) AS [Total Units]

sqldf 仅返回一行，与 SQL 中使用的查询相同

sqldf only returning one row, same query used in SQL

sql

r

sqldf