>>Hi Mike,
>>
>>this is an interesting example.
>>
>>Here, if you add an index on BoIdBase for optimize the join,
>>with the projection subquery VFP can run more slowly,
>>because the VFP engine is not very smart
>>( the correct plan is that of build a intermediate group subquery on the join fields
>>and then join it with the update table )
>
>Wow, you understand VFP very deeply! What is a projection subquery?
>
>Thanks,
>
>Alex

It is not very particular
if Table has N columns, every selection that returns some of these columns it is a projection.

For an UPDATE, the projection is the SET's columns.
VFP9 support one projection's subquery only.

I have not written very well.

>> with the projection subquery VFP can run more slowly,
replaced
with the projection's subquery VFP can run more slowly,