select modified_by,
(case
when modified_by = (select modified_by
                   from rxc.received_dcis
                   where clinical_study_id = 40613
  		   and RECEIVED_DCI_STATUS_CODE like 'REMOVED'
		   and patient like '01%'
                   group by modified_by
                   having count(received_dci_id) = (select max(cnt)
                                          	    from (select modified_by,  count(received_dci_id)cnt
                                                    from rxc.received_dcis
                                                    where clinical_study_id = 40613
                                                    and RECEIVED_DCI_STATUS_CODE like 'REMOVED'
			                            and patient like '01%'
                                                    group by modified_by)))
then (select max(cnt)
       from (select modified_by,  count(received_dci_id)cnt
             from rxc.received_dcis
             where clinical_study_id = 40613
             and RECEIVED_DCI_STATUS_CODE like 'REMOVED'
             and patient like '01%'
             group by modified_by))
end)"Pt 1"
from rxc.received_dcis
group by modified_by
/

then (select max(cnt)
             *
ERROR at line 16:
ORA-00979: not a GROUP BY expression