Re: Data model for a web messaging application.

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From: Itai (itaitai2003_at_yahoo.com)
Date: 10/05/04 

Date: 5 Oct 2004 06:19:04 -0700

Uri, John and especially David! Thanks for the code review; I am now
one step further :)

"John Bell" <jbellnewsposts@hotmail.com> wrote in message news:<41605341$0$21630$afc38c87@news.easynet.co.uk>...

> There is probably a
> natural key of RecipientID, SenderID, and SubmitDate so a covering unique
> index may be useful, and a INT may not be sufficient for you messageid.

"Covering index" is something I lack to understand ... How is it
stored in a
b-tree structure, does the whole string composed of the diffrent
columns get saved as one key in each node? How does SQL server
(depending on the query's' where clause of course) 'extracts' the
right column and scan for its appropriate value within the index? What
are the questions to ask when considering a covering index as a design
requirement.

Regarding the INT data type for messageID, what would you suggest?
Messages will often be deleted but the counter value will always
progress...

I thought about using a uid, but they are not suitable for a Clustered
Index since they are not guaranteed to be chosen in incremental
order...

Thanks again

-Itai

BTW does anyone know how to dump a table to a text file using command
line with arguments?