SQL & PL/SQL

i would like to ask how can i select top 1 record from the selected resultset to and then output as list in pl/sql
it is because i always retrieve two or more record from the resultset. my sql like belows:

select id from customer where surname ='WONG';

it returns:

2
3
4

in fact the table contain id 1,2,3,4

i have tried select id from customer where surname='WONG' and rownum=1;
it always return id=1, how can i select top 1 from resultset , in this case, id=2