masotti skriver:

> On 16/12/2010 15:39, Kjell Rilbe wrote:
> >> 5. The table has several indices, on one column each, one of which is a
> > PK. There are 18 columns, 9 of which have an index. 7 of the indices
> > have selectivit < 0.0006, one has 0.5 and one has selectivit 1. The 0.5
> > index will become more selective later on while the 1.0 one will
> > probably keep having over 99% nulls, but be very useful for the records
> > where the indexed column is not null.
>
> I'm wandering if in such a case, theorically, it's not better to have
> two (or more) tables and then SELECTing from a VIEW with a UNION ALL of
> them when absolutely there is a need of other types of filtering.
>
> I mean: a table with a million row with the same NULL value in a field
> (say FLD_X) that has low chances to change his value and a trigger in
> the view can delete from a table and insert in the other when the value
> changes: as an example this sould be like a status field, that show
> progress in a particular phase of work. Often searches are for pieces in
> a specific phase and then you can select directly from the real table
> and not from the generic view.
>
> What are the lòimits in a solution like that (I suppose a field that
> changes very very rarely and with low risk of conflicts)?

Interesting idea, but seems like a lot of work for a somewhat smallish
gain. :-)

Kjell
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Kjell Rilbe
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