Re: primary and foregin keys
Date: 26 Dec 2004 06:54:00 -0800
Message-ID: <1104072840.001643.114140_at_f14g2000cwb.googlegroups.com>
>> We all know that there are some exceptions, most notably a well
known approach to open a new SALES table every quarter, then purge old
data
by dropping the oldest one. <<
No, we don't.
That particular design flaw is called "attribute splitting" , in this case on a temporal value. You can also look up what Chris Date and Dave McGovern have to say about this under orthogonal design.
Newbies do this because this is how they stored physical magnetic tape files. The labels in the IBM systems were labelled with "yyddd" codes that blew up in 2000. Since you do not do random searching on a tape, you had to keep the current data PHYSICALLY separated.
In an RDBMS, all the current data would be in one table, VIEWs would provide quarterly summaries and the old data would be moved to the data warehouse, never purged. Tables are not files. Received on Sun Dec 26 2004 - 15:54:00 CET