test:

c1 c2

1 a

1 b

2 c

select
to_char(wmsys.wm_concat(c2)) ,
to_char(replace(wmsys.wm_concat(c2),',','/'))

from
test

group by
c1

show case:

1 a,b a/b

2 c c

同样的功能函数：

select listagg(c2,',') within group(order by c1) from test ;