Sammenkæd og grupper flere rækker i Oracle

Overvej at bruge LISTAGG-funktionen, hvis du er på 11g:

select grp, listagg(name,',') within group( order by name ) 
  from name_table group by grp

sqlFiddle

upd: Hvis du ikke er det, så overvej at bruge analyser:

select grp,
    ltrim(max(sys_connect_by_path
       (name, ',' )), ',')
        scbp
  from (select name, grp,
            row_number() over
           (partition by grp
            order by name) rn
         from tab
          )
start with rn = 1
connect by prior rn = rn-1
and prior grp = grp
  group by grp
  order by grp

sqlFiddle