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Posted by Tommy Hayes on 09/25/07 16:36
Thanks again Roy,
Tommy.
On Sep 25, 3:08 pm, "Roy Harvey (SQL Server MVP)"
<roy_har...@snet.net> wrote:
> I would be inclined to cluster (unique) on the datetime/identity pair,
> in that order, and set the PK on the identity non-clustered. That
> gives you the date range efficiency you need.
>
> I can see no benefit to clustering on the identity. There is no way
> to tell the optimizer that the two columns are moving along "in
> parallel" the way they are, so don't worry about it.
>
> Roy Harvey
> Beacon Falls, CT
>
> On Tue, 25 Sep 2007 13:57:37 -0000, Tommy Hayes
>
>
>
> <tommy.ha...@gmail.com> wrote:
> >Hello all,
>
> >We have a table with about 2 million rows that is used to store log
> >events. The table has an identity column and also a datetime column to
> >record the event time. It is expected to at least double in size over
> >its lifetime. Because the datetime records the current time, the value
> >of that column goes up as the value in the identity column goes up.
>
> >When doing searches on the table it is normal to have a date range as
> >part of the search. This would lead me to think that the clustered
> >index of the main table should be on the datetime column, letting SQL
> >Server know that a date range is sequential in the table as opposed to
> >the database server hopping all over the place to retrieve rows.
>
> >However is there any argument for putting the clustered index on the
> >identity column of the main table? The datetimes may not be unique
> >(highly unlikely in the given application, but logically possible I
> >guess) - would that lessen the advantage of the clustered index on the
> >datetime?
>
> >How about putting the clustered index on the identity column, and if
> >given two dates to form a range then look up the two corresponding
> >identities and turn the query into an indentity range query, thus
> >allowing the identity column clustered index to be used for the date
> >range query as well?
>
> >Or is there some way to let SQL Server know that two columns are
> >'linked' so that it knows to alter the query itself? (i.e. a range on
> >column A is equivalent to a range on column B, and column B is the
> >clustered index column)
>
> >Any ideas would be appreciated.
> >Thanks,
> >Tommy.- Hide quoted text -
>
> - Show quoted text -
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