Oracle ROWTOCOL Function oddities - database

Question

I have a requirement to pull data in a specific format and I'm struggling slightly with the ROWTOCOL function and was hoping a fresh pair of eyes might be able to help.
I'm using 10g Oracle DB (10.2) so LISTAGG which appears to do what I need to achieve is not an option.
I need to aggregate a number of usernames into a string delimited with a '$' but I also need to concatenate another column to to build up email addresses.
select
rowtocol('select username_id from username where user_id = '||s.user_id|| 'order by USERNAME_ID asc','#'||d.domain_name||'$')
from username s, domain d
where s.user_id = d.user_id
(I've simplified the query specific to just this function as the actual query is quite large and all works except for this particular function.)
in the DOMAIN Table I have a number of domains such as 'hotmail.com','gmail.com' etc
I need to concatenate the username, an '#' symbol followed by the domain and all delimited with a '$'
such as ......
joe.bloggs#gmail.com$joeblogs#gmail.com$joe_bloggs#gmail.com
I've battled with this and I've got close but in reverse?!.....
gmail.com$joe.bloggs#gmail.com$joeblogs#gmail.com$joe_bloggs
I've also noticed that if I play around with the delimiter (,'#'||d.domain_name||'$') it has a tendency to drop off the first character as can be seen above the preceding '#' has been dropped from the first email address.
Can anyone offer any suggestions as to how to get this working?
Many Thanks in advance!

Answer 1

Assuming you're using the rowtocol function from OTN, and have tables something like:
create table username (user_id number, username_id varchar2(20));
create table domain (user_id number, domain_name varchar2(20));
insert into username values (1, 'joe.bloggs');
insert into username values (1, 'joebloggs');
insert into username values (1, 'joe_bloggs');
insert into domain values (1, 'gmail.com');
Then your original query gets three rows back:
gmail.com$joe.bloggs
gmail.com$joe_bloggs#gmail.com$joebloggs
gmail.com$joe_bloggs#gmail.com$joebloggs
You're passing the data from each of your user IDs to a separate call to rowtocol, which isn't really what you want. You can get the result I think you're after by reversing it; pass the main query that joins the two tables as the select argument to the function, and have that passed query do the username/domain concatenation - that is a separate step to the string aggregation:
select
rowtocol('select s.username_id || ''#'' || d.domain_name from username s join domain d on d.user_id = s.user_id', '$')
from dual;
which gets a single result:
joe.bloggs#gmail.com$joe_bloggs#gmail.com$joebloggs#gmail.com
Whether that fits into your larger query, which you haven't shown, is a separate question. You might need to correlate it with the rest of your query.
There are other ways to string aggregation in Oracle, but this function is one way, and you already have it installed. I'd look at alternatives though, such as ThomasG's answer, which make it a bit clearer what's going on I think.

Answer 2

As Alex told you in comments, this ROWTOCOL isn't a standard function so if you don't show its code, there's nothing we can do to fix it.
However you can accomplish what you want in Oracle 10 using the XMLAGG built-in function.
try this :
SELECT
rtrim (xmlagg (xmlelement (e, s.user_id || '#' || d.domain_name || '$')).extract ('//text()'), '$') whatever
FROM username s
INNER JOIN domain d ON s.user_id = d.user_id