Oracle SQL escape character (for a '&')

Set the define character to something other than &

SET DEFINE ~
create table blah (x varchar(20));
insert into blah (x) values ('blah&amp');
select * from blah;

X                    
-------------------- 
blah&amp 

|| chr(38) ||

This solution is perfect.

the & is the default value for DEFINE, which allows you to use substitution variables. I like to turn it off using

SET DEFINE OFF

then you won't have to worry about escaping or CHR(38).

insert into AGREGADORES_AGREGADORES (IDAGREGADOR,NOMBRE,URL)
values (2,'Netvibes',
'http://www.netvibes.com/subscribe.php?type=rss' || chr(38) || 'amp;url=');