Prueba esto si estás usando Oracle 11g
SELECT
C1,
LISTAGG(C2, ',') as C2,
C3
from
tbl
GROUP BY
C1,C1
Prueba esto si estás usando Oracle 11g
SELECT
C1,
LISTAGG(C2, ',') as C2,
C3
from
tbl
GROUP BY
C1,C1