Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!pt.cs.cmu.edu!andrew.cmu.edu!bg0l+
From: bg0l+@andrew.cmu.edu (Bruce E. Golightly)
Newsgroups: comp.databases
Subject: Re: Relational Model
Message-ID: <8YnkJyy00WB2ABX8IL@andrew.cmu.edu>
Date: 27 Jul 89 12:52:14 GMT
Organization: Carnegie Mellon, Pittsburgh, PA
Lines: 19

You need to be careful with the UNIQUE atribute. We had/have a considerable
problem in this area.

We converted our Telecommunications billing system to a relational database
a couple of years ago. One of the things that nearly drove us nuts during
the development was an attempt to duplicate output from an old COBOL based
system. We were loosing records.

We eventually discovered that the records being "lost" were being eliminated
by the data base as duplicates. (NOTE: The dropping of dups here was the
result of a poorly written WHERE clause) One examination, these records
were found to be identical to any number of decimal places you care to name.
It turns out that the granularity available within certain long distance
operations is not fine enough to distinguish between two calls from the
same phone to the same phone within a short period of time.

And they wonder why my hair is turning grey and falling out!

Bruce