problem - group by

Hello,

in SQLite this query is posible:

SELECT acount/1000, SUM(values)  FROM acounts
GROUP BY acount/1000

this very simple and elegant way to get groups of common acounts, Unfortunately Postgres doesn't alow "GROUP BY
acount/1000"- only "GROUP BY acount", which is not the same. 

I know, there are several ways, how to solve this problem, but the metod "GROUP BY acount/1000" seems to be the most
elegant.Can anyone help me? 

Thanks Dusan