> it would have used the TransactionNo index to rapidly locate the few TransactionItem records associated with each Transaction.
>
> For example
>
> Select * from TransactionItems TI
> where TI.TransactionNo in (Select TransactionNo from Transactions
> where PersonNo = 200)
>
> TransactionNo is an indexed field of TransactionItems
>
> Is this the right way to approach this?

Not quite. Better approach could be join+distinct or execute
block+for select. But all depends on number of records in tables and
result sets of both queries.

SY, SD.