Oracle 21c

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CREATE TABLE mytable (
  col1 varchar(10)
);


insert into mytable
select 'ID1' from dual union all
select 'ID2' from dual union all
select 'ID3' from dual union all
select 'ID4' from dual union all
select 'ID5' from dual union all
select 'ID6' from dual union all
select 'ID7' from dual ;
7 rows affected

select col1, CEIL(row_number() over (order by col1)/2) as grp
from mytable


COL1
GRP


ID1
1

ID2
1

ID3
2

ID4
2

ID5
3

ID6
3

ID7
4


with cte as (
  select col1, CEIL(row_number() over (order by col1)/2) as grp
  from mytable
)
select LISTAGG(col1, ',') as list
from cte
group by grp
order by grp


LIST


ID1,ID2

ID3,ID4

ID5,ID6

ID7