sql输出文件包含空值，但我在select语句中使用isnull，这里是我的代码。对于modifier1和modifier2列，我的输出文件中仍然有空值。

Select 
    A.SvcProvSvcId as 'CDMCode',
    A.BillName,
    A.[CPT/HCPCSCdVal],
    isnull(A.[Modifier 1],'') as Modifier1,
    isnull(A.[Modifer 2],'') as Modifier2,
    A.RevCdVal,
    A.Price

into ##temp_CDM

From ##temp_CDMAllPrices A

inner join 
    (select max(isnull(LastRateChange,getdate())) Last_Price_Chng,ExtrnId,SvcProvSvcId from ##temp_CDMAllPrices group by ExtrnId,SvcProvSvcId) B 
    on A.ExtrnId = B.ExtrnId 
        AND A.SvcProvSvcId = B.SvcProvSvcId
        AND isnull(A.LastRateChange,getdate()) = B.Last_Price_Chng

DECLARE @FileLocation varchar(255)
DECLARE @OutputFile varchar(255)
DECLARE @FileName varchar(255)
DECLARE @strCommand varchar(8000)

SET @FileLocation = '\\server\LoadFiles\'
SET @OutputFile = 'ExperianCDM'
SET @FileName = @FileLocation + LTRIM(RTRIM(@OutputFile)) + '.txt'  
SET @strCommand = 'bcp "SELECT * from [server].[Database].[##temp_CDM]" queryout ' + @filename +' -t "|"  -c -T'

RAISERROR(@FileName, 0, 1) WITH NOWAIT
PRINT @strCommand

EXECUTE master.dbo.xp_cmdShell @strCommand

Drop Table ##temp_CDMAllPrices, ##temp_CDM