Is that field indexed?

Stevio wrote:

>Let me describe my problem with my Firebird database:
>
>Two tables:
>Book (33043 records)
>Borrower (1607 records)
>
>The first query took 21 seconds last time I ran it. The second query took
>less than 1 second. For the second query I removed one line that accessed a
>location field. This field is a location id field that can have 6 different
>values (1 to 6). In the book table, 25014 records have a value of 1 for this
>field.
>
>Why does this line increase the speed of the query so much? Is there a way
>to work around this so that I can still restrict the query to take records
>with a value of 1 but without the query taking so long?
>
>QUERY 1 (slow!)
>------------------
>SELECT
> B.BORROWER_ID,
> BR.NAME
>FROM
> BOOK B,
> BORROWER BR
>WHERE
> B.BORROWER_ID = BR.BORROWER_ID AND
> B.DATE_DUE_BACK IS NOT NULL AND
> B.DATE_DUE_BACK >= '05/10/2002' AND
> B.DATE_DUE_BACK <= '06/07/2002' AND
> B.LOCATION_ID = 1
>GROUP BY
> B.BORROWER_ID,
> BR.NAME
>ORDER BY
> BR.NAME
>
>QUERY 2 (fast! - the blank line is the difference between the two queries)
>------------------
>SELECT
> B.BORROWER_ID,
> BR.NAME
>FROM
> BOOK B,
> BORROWER BR
>WHERE
> B.BORROWER_ID = BR.BORROWER_ID AND
> B.DATE_DUE_BACK IS NOT NULL AND
> B.DATE_DUE_BACK >= '05/10/2002' AND
> B.DATE_DUE_BACK <= '06/07/2002'
>
>GROUP BY
> B.BORROWER_ID,
> BR.NAME
>ORDER BY
> BR.NAME
>----------------------------
>
>Thanks!
>Stephen
>
>
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--
Thomas Miller
Delphi Client/Server Certified Developer
BSS Accounting & Distribution Software
BSS Enterprise Accounting FrameWork

http://www.bss-software.com