Re: pervasiveness of surrogate (also called synthetic) keys

Most of the old school accounting systems maintained an invoice line number.

> Invoice Line
>     -Invoice Number
>     -LineNo
>     -ItemID
>     -qty
>     -Price

The line number started from 1 (the first line on the invoice) on
every unique invoice.  This has the added benefit of allowing the
primary key index (invoice_no, line_no) allowing you to pull up the
invoice line records in correct order without requiring an extra sort
and, if you don't need any fields from the invoice, a join.

Compare the two queries pulling up invoice lines over a range of
invoice numbers.

merlin