create table gsm(gsmnumber varchar, newgsmnumber varchar);
 
insert into gsm values("0(534) 000 00 00 ", "");
insert into gsm values("(534) 000 00 00 ", "");
 
 
 update gsm set newgsmnumber=case when gsmnumber like '0%' then replace(replace(replace(gsmnumber,"(",""),")","")," ","") 
        else "0"||replace(replace(replace(gsmnumber,"(",""),")","")," ","")
        end;
 
select * from gsm;