create table test(phone_num) as
(
select '8297231486' from dual union all
select '900005452' from dual
)
Expected result:
(829) 723-1486
(900) 005-4527
My effort
select concat('(',substr(phonenum,1,3),')',substr(phonenum,4,3),'-',substr(phonenum,7) as num_formatted from test