Utilisation de group by dans une fonction pl sql

create or replace
package body   non_val is  

function  get_non_val(p_id in number default 1, 
                            p_date_ref in date default sysdate, 
                             p_seg1 in varchar2, 
                             p_seg2 in varchar2, 
                             p_seg3 in varchar2)      
                        
                         return number is v_qnt number;
                             

begin
select SUM(mmt.TRANSACTION_QUANTITY) AS TRANSACTIONP
  into v_qnt
      from MTL_MA mmt, 
          mtl_s msi,
          mtl_pas mp,
          mtl_v micv 

            where 
              msi.IN_ID = mmt.INV_ID

              and mmt.ORGANIZATION_ID = mp.ORGANIZATION_ID
              and msi.ORGANIZATION_ID = mp.ORGANIZATION_ID

              and micv.inv_id = msi.inv_id 
              and micv.organization_id = msi.organization_id
            

                and trunc(mmt.transaction_date) <= TRUNC (p_date_ref)
                and  msi.organization_id =p_id 
                and msi.segm1=p_seg1
                and msi.segm2=p_seg2
                and msi.segm3=p_seg3
                group by msi.SEGM1||'.'||msi.SEGM2||'.'||msi.SEGM3,
                          mmt.ORGANIZATION_ID,
  
                           mmt.INV_ID,
                            msi.des,
                                                msi.SEGM1||'.'||msi.SEGM2,msi.segm3,
                            msi.SEGM2,
                          mp.attribute6
               having SUM(mmt.PRIMARY_QUANTITY) <> 0;



Exception 
When No_data_found Then 
null;
return nvl(v_qnt,0);

END get_non_val;





END non_val;