On 1-12-2012 09:53, Dmitry Yemanov wrote:

> 01.12.2012 1:26, Leyne, Sean wrote:
>>
>> In order for an index to be used for ORDER BY, the sort order much match
>> exactly the storage order of the index.
>
> Correct.
>
>> All indexes have NULLs stored at the end (ie. not first).
>
> ASC indices have NULLs stored in the beginning, DESC indices have NULLs
> stored at the end.

For Firebird 2.x yes, but for Firebird 1.x no:
http://www.firebirdsql.org/file/documentation/reference_manuals/user_manuals/html/nullguide-sorts.html
--
Mark Rotteveel