Walter,

Let me re-respond. I've just re-read my original post.

What I meant, but may have not made clear.

When you open an ISAM table to make an update, you may or may not be required to examine every record in that table in order to properly position the record pointer. The same thing applies when sending updates back to the table.

With an RDMS, such as SQL Server, you access and update only the records that meet a given criteria. This is not the same as having to access to the entire table.