Re: Why is "group by" obligatory in SQL?
Date: Fri, 24 Jul 2009 14:04:08 -0300
paul c wrote:
> Cimode wrote:
> Great post, Cimode, Djikstra as profound as ever, this stuff bears
> repeating every so often.
Dijkstra is da bomb!
> Too bad so little remains of the history of
> db language development from the 1970's, I think there are still lessons
> to be learned from the scanty archives. The motivations of those days
> must be murky to anybody who didn't grow up with assembler languages, in
> fact I'd say they remaiin murky for most of the people who were there.
> In the commercial world of that time there was a
> lot of emphasis on so-called 'structured programming techniques', which
> we know today is just a form of language mysticism, at least insofar as
> it disguises the real programmer's interface.
Did you intend the irony?
> Another quote from the McJones site is from Don Chamberlin:
> "I had a conversion experience, and I still
> remember this. Ted Codd came to visit Yorktown, I think it
> might have been at this symposium that Irv alluded to. He
> gave a seminar and a lot of us went to listen to him. This
> was as I say a revelation for me because Codd had a bunch
> of queries that were fairly complicated queries and since I’d
> been studying CODASYL, I could imagine how those
> queries would have been represented in CODASYL by
> programs that were five pages long that would navigate
> through this labyrinth of pointers and stuff. Codd would sort
> of write them down as one-liners. These would be queries
> like, “Find the employees who earn more than their
> managers.” [laughter] He just whacked them out and you
> could sort of read them, and they weren’t complicated at all,
> and I said, “Wow.” This was kind of a conversion
> experience for me, that I understood what the relational
> thing was about after that."
Chris Date once related a story from the early days of the relational model. He and Codd often spoke at various "User Group" meetings. He described one in California where the user group had divided into working groups to tackle the 5 "big problems" in databases.
Each working group was basically researching the best, most efficient way to write a query program for an important query recognized as very difficult to write.
After Codd gave his regular talk, someone asked what the solutions to these 5 big problems would look like in a relational language so Codd wrote them down in Alpha. Each was a one-liner.
According to Chris, a lot of the early big names in databases were there. The presentation had a profound effect on everyone attending and influenced a lot of them to pursue relational database management systems leading to the creation of all the big vendor companies.
I suspect it is the same meeting Chamberlin described in the mcjones quote. Received on Fri Jul 24 2009 - 19:04:08 CEST