[AccessD] Joining Tables

On Saturday 11 October 2008 02:27:40 Arthur Fuller wrote:
> I would go even further, Charlotte. Unless the underlying table' column has
> a large degree of uniqueness, chances are good that the optimizer will do a
> full table scan anyway. In this case, the index in question would be time
> well wasted, since the system will be forced to maintain the index while
> also never using it. (At least that is the case in SQL Server; I cannot
> verify that the same is true in JET.
>
> Arthur
>
> On Fri, Oct 10, 2008 at 12:40 PM, Charlotte Foust <
>
> cfoust at infostatsystems.com> wrote:
> > Of course, if you are dealing with a Yes/No field, there's no point in
> > indexing it since it can only have one of 2 or 3 values.
> >
> > Charlotte Foust

To go even further, it depends.

Scenario 1) either table has a reasonable degree of uniqueness on the join 
column ==> assumtion,  indexing will be picked up by the optimiser as a 
preferred mechanism.

Scenario 2) one of the two tables has a fair degree of uniqeness and the other 
cant be fairly keyed on that column

Scenario 3) the query is run once a year.

It depends.

ymmv
Bruce