subset data based on particular values in oracle -

i trying make copy of file particular columns appears twice. need both entries in separate file. attached below code written not able read list of id on needs subset

create table duplicateclientid_avox select * nodup_avox_data_v1_nr client_id =(select client_id (select client_id, count(client_id) clientcount  nodup_avox_data_v1_nr group client_id having count(client_id) > 1)); 

perhaps try using in() so:

create table duplicateclientid_avox select * nodup_avox_data_v1_nr client_id in (                      select client_id                      nodup_avox_data_v1_nr                      group client_id                      having count(client_id) > 1                     );