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  3. April 2007

Re: SQL, Logical Files, Unions & Indexes.

HI there
Well I guess if you have to segregate your data into separate libraries (and a reasonable explanation for this is separate companies wanting pseudo physical separation of their data) then why not run separate queries for each library - possibly even in parallel - and then aggregate (or whatever) the data afterwards ?
My experience has been that you don't generally want random access to the files in different libraries, but when the need arises it is usually for extraction and creation of statistical and summary data.
I grant you that this probably needs some additional work up front to set up but might well be a good/better performer.
Maybe if you could give me an example of a task that required you to read the whole table as a single query I could see what you're getting at. 

regards
Evan Harris

At 08:53 a.m. 2/04/2007, you wrote:


Birgitta,

in the original message Mike talked about an Index over a series of
analogous tables in different libraries.
He stated that it's not possible to create an index over all the tables, and
I don't know of any way either.
(or is there ?) .
As you mention "with the right indexing strategie SQL performs much better
than natibe I/O" .
Therefore it should be possible to create indexes over multiple tables, just
as it is possible to make logical files over multiple files? .
(I cannot see how views, without indexes, are more powerfull than  logical
files)

So the only solution at the moment -as I see it, the same that Mike
suggested,-
is to create a DDS described Logical file over all these tables (or PFs).
In this case I don't see another way but
"A DDS described logical file has to be used in the SQL-statement ".
and therefore
"with the logical (the one over all the tables) the new SQE will not be
used" .

Any suggestions or alternatives are more than welcome.

luc

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