Generating comma-separated lists in Oracle

generating comma-separated lists in oracle is much simpler than in SQL Server. In Oracle 11g, LISTAGG function can be used:

SELECT authors.au_id, LISTAGG(titleauthor.title_id, ', ')
WITHIN GROUP (ORDER BY titleauthor.title_id) as TitleIds 
FROM titleauthor JOIN authors USING(au_id)  
GROUP BY authors.au_id