--- In firebird-support@yahoogroups.com, Robert martin wrote:

> Hi All
>
> I have a Query that is basically
>
> SELECT a,b,c
> FROM Table1 t1
> JOIN Table2 t2 t2 ON t2.pk = t1.FK
> WHERE t1.PK = 4
> AND t2.CancelFlag <> 'T'
>
> The final and clause (t2.CancelFlag <> 'T' ) is really slowing the
> query down. It takes 1.3s with and is near instantaneous without.
> The CancelFlag field is a Char(1) field that is NOT indexed (because
> it would have low selectivity). Is there anything I can do to speed
> up this query?
>
> In the data I am testing the table sizes are...
> t1 = 3100
> t2 = 72000

OK Rob, I want you to try two things to tame your query!

First, try to eliminate parts of your query that may include indexed
fields that you do not want to be part of any plan:

SELECT a,b,c
FROM Table1 t1
JOIN Table2 t2 t2 ON t2.pk = t1.FK
WHERE t1.PK = 4
AND (2=0 or (<the rest of the where clause))

Secondly, prevent the query from using two indexes on t1:

SELECT a,b,c
FROM Table1 t1
JOIN Table2 t2 t2 ON t2.pk = t1.FK+0
WHERE t1.PK = 4
...

If neither of these two suggestions help (even when taken together),
then I'm stumped.

HTH,
Set