Give an alias to the derived tableSELECT dtl_doccode, dtl_prodid, sum(TotalItems)FROM(SELECTdtl_doccode,dtl_prodid,dtl_prodquantity,uomd_packing,TotalItems = dtl_prodquantity * uomd_packingFROM tblDocumentDetailsInner Join tblProducts ON tblDocumentDetails.DTL_ProdId = tblProducts.PROD_IdInner Join tblDocuments ON tblDocumentDetails.DTL_DocId = tblDocuments.DOC_IdInner Join tbluomdetails On tblDocumentDetails.dtl_produomdid = uomd_idWHEREtblDocumentDetails.DeletedFlag = 0AND DOC_TypeId = 20AND DTL_DocId = 451AND PROD_Id = '17') aGROUP BY dtl_doccode, dtl_prodid
KH