On 29-7-2014 09:47, Svein Erling Tysvær
svein.erling.tysvaer@... [firebird-support] wrote:

> Don't know whether windowing functions can be used in the WHERE clause, but when Firebird 3 is released, it would be tempting to try things like
>
> WHERE MOD(ROW_NUMBER() OVER (ORDER BY <something>), 5) = 2

You shouldn't be able to use window functions in a `WHERE`, only in the
`SELECT` columnlist. The `ROW_NUMBER` is applied over the materialized
rows, so you can't apply it in the filtering condition. You need a
subquery or CTE with `ROW_NUMBER()` and then filter that in the outer
select.

Mark
--
Mark Rotteveel