> I've following SQL statement:
>
> select L_ID, L_NUMBER, lt.LT_TIMESTAMP as START_TIME
> from L_TABLE
> left join L_TABLE_SLAVE lt on lt.LT_L_ID = L_TABLE.L_ID and lt.LT_EVENT_ID = 1
> where L_TABLE.L_ID > 177700
>
> I'd like to limit search resutl on to rows where START_TIME is null.
> However my first idea ".. AND START_TIME IS NULL" doesn't work, but
> second guess ".. AND lt.LT_TIMESTAMP IS NULL" works.
>
> Is it possible to use use "START_TIME" in query at all?
>
> I'm using Firebird 2.0.4 with this one.

Not supported in Firebird 2.0, but it is supported in Firebird 2.1. The
same goes for GROUP BY. Very handy e.g. when you have some kind of
longish CASE statement in the field list. Although, you also can ORDER
BY the field index since ages.

In your case:

select L_ID, L_NUMBER, lt.LT_TIMESTAMP as START_TIME
from L_TABLE
left join L_TABLE_SLAVE lt on lt.LT_L_ID = L_TABLE.L_ID and
lt.LT_EVENT_ID = 1
where L_TABLE.L_ID > 177700
order by 3


But I don't like that as a permanent solution, because just in case the
field list gets extended before the field in question, you also have to
adjust the ORDER BY clause accordingly. Something one might miss when in
hurry. ;-)




--
Best Regards,
Thomas Steinmaurer
LogManager Series - Logging/Auditing Suites supporting
InterBase, Firebird, Advantage Database, MS SQL Server and
NexusDB V2
Upscene Productions
http://www.upscene.com
My blog:
http://blog.upscene.com/thomas/