Hi,
in this case Firebird will NOT use both part of index, please try it.
How will FB navigate by this index ?
normaly engine using only first part in this case (save part of time,
teoreticaly 50%).

example:
index (bDate, eDate);

SELECT * FROM table WHERE :iDate>= bdate AND :iDate<=eDate;

Firebird will navigate from begin of table to iDate by "bDate index" and
eDate will test naturaly.
If you are create only bDate index you will get same performance with less
over head.

Final solution depens mainly on comparation MAX(eDate)-MIN(bDate) and
MAX(eDate-bDate).

Slavek

PS: Instead day, you can use week, month, year depending by your situation
for segmentation :).
PS2: People alive (eDate is NULL) can be handle simply.



-----Original Message-----
From: firebird-support@yahoogroups.com
[mailto:firebird-support@yahoogroups.com] On Behalf Of Leyne, Sean
Sent: Sunday, June 22, 2008 10:29 PM
To: firebird-support@yahoogroups.com
Subject: RE: [firebird-support] Optimal algorithm for inventory



Slavomir,

> Hi, a compound index is for nothing !
> This task is simple to describe, but hard to realize.
> The problem is because you are interesting in all
> record from interval and in this case you can
> use only one part of coumpond index.

I must completely and utterly disagree with all that you have said.

A compound index can and will be used by a properly constructed SQL
query.



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