SELECT DISTINCT tblReportInstances.InstanceID, tblReports.ReportID, tblReports.ReportName, tblReportInstances.DueDate
FROM tblReports LEFT JOIN tblReportInstances ON tblReports.ReportID = tblReportInstances.ReportID
GROUP BY tblReportInstances.InstanceID, tblReports.ReportID...