What's the alternative of Listagg in Netezza?

Question

SELECT ID FROM TABLE_A WHERE DATE >= CURRENT_DATE;

The output for the above query will be

001
002
003

I need the output as 001,002,003. I am trying below in Netezza but GROUP_CONCAT is not installed in database. This could be easily done in ORACLE using Listagg. But the group_concat & string_agg not working for me.

SELECT GROUP_CONCAT(ID,',') 
FROM (SELECT ID FROM TABLE_A WHERE DATE >= CURRENT_DATE) a;

Please help if we can do something only with normal sql without using any function.