afiedt.buf, why Oracle had the world's first commercial RDBMS even though it was based on IBM's System-R, why nobody ever used MTS. One thing it doesn't cover is why the DUAL table is so named. Now the reason for this appeared in an Oracle Magazine column a few years back. I clicked on my bookmark so I could forward the URL only to get a 404 error. Turns out there's been a recent purge of the Oracle Magazine online archive. I presume this is because of a desire to retire stale and potentially misleading information rather than because OTN is running out of disk space.
Fortunately the Wayback Machine still has a copy of the web page in question. But it is the Internet Archive only works if we know what and when we know what we are looking for. So, s a public service and to keep this information in a Google-isable domain, I reproduce the text here.
The History of Dual
In the November/December issue of Oracle Magazine you recount the history of the company, so I'm wondering if you can tell me how the DUAL table got its name. People I've asked, including seasoned Oracle gurus, have not been able to answer this.
Sean O'Neill
I created the DUAL table as an underlying object in the Oracle Data Dictionary. It was never meant to be seen itself, but instead used inside a view that was expected to be queried. The idea was that you could do a JOIN to the DUAL table and create two rows in the result for every one row in your table. Then, by using GROUP BY, the resulting join could be summarized to show the amount of storage for the DATA extent and for the INDEX extent(s). The name, DUAL, seemed apt for the process of creating a pair of rows from just one.
Chuck Weiss, Oracle
Source: Oracle Magazine "Sendmail column" January 2002
Update
In the Comments Marco Gralike linked to a thread on AskTom. That URL was broken by the migration of AskTom to a new version of ApEx. Here is the new URL for the thread.
