Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

From: Lauri Pietarinen <>
Date: Tue, 04 Mar 2003 08:32:03 +0200
Message-ID: <>

Jan Hidders wrote:

>>OK, point being that if SQL had not had duplicates from the start the
>>motivation for such research would have been much stronger, and we would
>>have got results sooner.
>Could be, but note that this would then be because you made things *harder*
>for the implementors and forced them to think about these issues.
Exactly, and as a result we would have better products. I would also affect how people thought and
used products. We would probably utilize views much more than now.  Updatable views, anybody?

>>>So it could very well that for this particular problem you are right.
>>Meaning that "you can do more optimisations with set's"?
>Meaning that in this case you might be right that for this particular query
>the bag-based approach makes optimization a bit harder. However, after
>giving it a bit more thought I doubt that even this is true. The problem is
>just as difficult in a set-only as in a bag-based approach. In both cases
>you can optimize a join followed by a project that projects out a certain
>table by using only the index for the "invisible" table.
Or ignoring it completely...

Your point is that if the user gives the 'DISTINCT' keyword, it works as if it was a set-based system.

>Ah, wait, I hadn't really seen the appendix in part II. It's really Chris
>Date at his worst. After reading such nonsense it always takes me a day or
>two to take him serious again. For starters he seems to miss the essential
>point that the presented algebra is an internal algebra. When I read his
>remark about "classical relational algebra" I can only conclude that he is
>the one who doesn't know the literature. On all the conferences I have been
>I have heard this phrase used and everybody knew exactly what it meant. But
>no, Chris Date is going to explain to everyone what these words really mean.
>I can only describe that as hubris.
OK, no comments on that.

Lauri Pietarinen Received on Tue Mar 04 2003 - 07:32:03 CET

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