How does VFP optimize a query when using join clauses?

I have to get data from 2 children tables. The link is via the parent.

Parent : SoHeader has customer ship to # and SoNo and CustNo
Child1 : SoTrans has what was ordered, and SoNo
Child2 : CustAddr has Customer ship to address.

I need to get $s and # of units totals from SOTrans, and group them by each ship to location.

So do you start at the parent, or a child in the SQL when using joins?

TIA

__Stephen Russell