Count Returning blank instead of 0

问题:

Good day everyone here is my code

SELECT 
    'Expired Item -'+ DateName(mm,DATEADD(MM,4,AE.fld_LOAN)) as [Month]
    ,COUNT(PIT.fld_ID)'COUNT'
    ,SUM (PIT.fld_GRAM)'GRAMS'
    ,SUM (PH.fld_AMNT)'PRINCIPAL'
FROM  #AllExpired AE
    INNER JOIN Transactions.tbl_ITEM PIT
    ON AE.fld_MAINID=PIT.fld_MAINID
    INNER JOIN Transactions.tbl_HISTO PH
    ON AE.fld_MAINID =PH.fld_MAINID
GROUP BY DATENAME(MM,(DATEADD(MM,4,AE.fld_LOAN)))

the problem I'm facing is that my Count function does not return 0 if it has no values, Sum function does not return NULL if there are no resulting values retrieved, instead it just output blank, why is that so? and how can i fix it?

here is a screen shot of sample output

ofcourse this is not i want i want it to output zero and nulls. please help me i do not know whats wrong. thank you.

回答1:

You cannot expect any records to be outputted when using a GROUP BY clause, when no records exist in your source.

If you want an output of 0 from the SUM and COUNT functions, then you should not use GROUP BY.

The reason is that when you have no records, the GROUP BY clause have nothing to group by, and then is not able to give you any output.

For example:

SELECT COUNT(*) FROM (SELECT 'Dummy' AS [Dummy] WHERE 1 = 0) DummyTable

will return one record with the value '0', where as:

SELECT COUNT(*) FROM (SELECT 'Dummy' AS [Dummy] WHERE 1 = 0) DummyTable
GROUP BY [Dummy]

will return no records.

回答2:

I would imagine you need to change your joins from INNER to OUTER to ensure rows are returned even when there is no corresponding record in tbl_PawnItem -

SELECT 
    'Expired Item -'+ DateName(mm,DATEADD(MM,4,AE.fld_LoanDate)) as [Month]
    ,COUNT(PIT.fld_PawnItemID)'COUNT'
    ,SUM (PIT.fld_KaratGram)'GRAMS'
    ,SUM (PH.fld_PrincipalAmt)'PRINCIPAL'
FROM  #AllExpired AE
    LEFT JOIN Transactions.tbl_PawnItem PIT
        ON AE.fld_PawnMainID=PIT.fld_PawnMainID
    LEFT JOIN Transactions.tbl_PawnHisto PH
        ON AE.fld_PawnMainID=PH.fld_PawnMainID
GROUP BY DATENAME(MM,(DATEADD(MM,4,AE.fld_LoanDate)))

回答3:

Perhaps #AllExpired is empty, or one of the joins returns no results?

Remember inner joins need results on both sides in order to return, so because #AllExpired is empty the join returns nothing.

Change it to an OUTER join.