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Re: Clusters physical representation

From: <markp7832_at_my-deja.com>
Date: Fri, 24 Dec 1999 22:05:26 GMT
Message-ID: <840qia$q3d$1@nnrp1.deja.com>


In article <840jbe$li9$1_at_nnrp1.deja.com>,   markp7832_at_my-deja.com wrote:
> In article <OtL84.113$uG.4165_at_news.siol.net>,
> "Miha ®nidar¹iè" <miha.znidarsic_at_ixtlan-team.si> wrote:
> > Can someone please explain me physical representation of Clusters
> (Cluster
> > organized tables). How and where the PrimaryKey is stored, how are
> other
> > datas? etc
> >

...removed quote from concepts manual and sequential file example...
>
> There are two kinds of clusters, indexed and hash. The cluster index
> can be stored in any tablespace you want to assign it to. Preferably
a
> tablespace devoted to indexes. You can not access the cluster unless
> the cluster index exists. The cluster index is like any other index.
>

........ stuff about hash
>

My statement about the index needs a little more explanation so let us make that read. The cluster index is like any other index except that it will store a cluster key value only once since it points to the block (or first block in a set of chained blocks) that hold all rows with a cluster key value. Cluster indexes also store nulls keys where in a normal there are no entries for null keys. Each table in a cluster may have a primary key that is or is not the cluster index.

Example. Cluster the emp and dept tables on dept_no. The emp table would have a primary key on emp_no while dept would have its primary key on the cluster key, dept_no.
--
Mark D. Powell -- The only advice that counts is the advice that  you follow so follow your own advice --

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Before you buy. Received on Fri Dec 24 1999 - 16:05:26 CST

Original text of this message

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