SQL & PL/SQL :: Query To Convert Rows Into Column

I need a single select query which converts all the rows into a single value . Below is my requirement :

Create table email_tbl(emailid varchar2(30));
insert into email_tbl('1@y.com');
insert into email_tbl('2@y.com');
insert into email_tbl('3@y.com');
insert into email_tbl('4@y.com');

Now , I need a single select query which gives me the below results.

1@y.com,2@y.com,3@y.com,4@y.com

I have done the above by using a cursors in the pl/sql objects.But want to achieve this with a single sql/query.