Re: DATA BLOCK

Nuno Souto <nsouto_at_optushome.com.au.nospam> wrote:
>Luis Nobre doodled thusly:
>
>>Can anyone please explain me how a block may contain rows from more than one table?
>>
>
>IIRC, the following is possible:
>
>- clustered tables. These used to be in <= 8.0. I believe they are
>still available in 8i if not 9i?

They're available, but no essentially no new features have been added since 7.3.something, for example you can't partition them. This is a great shame, since they're an ideal solution for some problems. Oracle uses several clusters for storing internal tables. Try :

SELECT table_name,cluster_name
FROM all_tables
WHERE cluster_name IS NOT NULL;

(as a privileged user, of course)

And indeed, clusters are the reason for a block being able to contain rows from multiple tables.

>I think nested tables can also physically share the same block, but
>don't quote me on that: only used them once and it was such a small
>data set anyway it didn't matter what the physical allocation would
>be, so I didn't bother checking...

Hm... I've never used nested tables in anger, but the Storage Internals course notes say "Nested tables are stored in a separate table called the store table", they don't mention in-line, as they do for VARRAY and LOBs.

-- 
Andrew Mobbs - http://www.chiark.greenend.org.uk/~andrewm/