Numeric cell with 0 not null
Use NVL().

 SELECT NVL(SUM(CANTITATE),0)
             FROM ANEXA2A_TABEL2_ROWS
            WHERE TIP_ACTIUNE = 'COLECTATE'
                  AND TIP_AMB = 'STICLA'
                  AND COD LIKE '%*';


That'll make the SUM() function return 0 if it would ordinarily return NULL.