In is slow.

Better to optimize the query like this:

Select o.*

From orders o

Inner join

(

                Select

                                p.Partid

                From

                                Partners p

                Where

                                p.country = SPAIN

}as partidentity

On partidentity.Partid = o.PartID

Which should be faster than a straight join i.e

Select o.* from orders o inner join partners p on p.Partid = o.partid

Where p.country = SPAIN

Jez