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  What's in a Condition?
Subject:   This is a bit scary ...
Date:   2002-10-02 12:39:50
From:   autarch
I will confess that for quite a while, when I first started working with databases, I did not really understand that joins weren't just another part of the where clause.

But they're not even remotely such a thing and frankly, I find it disturbing that someone billed as an "editor specializing in database and programming titles" might lack that fundamental knowledge about what relational databases are all about. This ignores, of course, that there are no truly relational products out there, including Oracle. Rather, they're all SQL databases, and SQL isn't truly relational.

I think it behooves someone editing books about databases to understand that difference. It's pretty sad that I didn't know this for so long, but anyone involved in the creation of database books should have a pretty solid understanding of relational theory.

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Showing messages 1 through 3 of 3.

  • John W. Adams photo This is a bit scary ...
    2002-10-03 05:55:48  John W. Adams | O'Reilly Blogger [View]

    I think you are confusing the persona in which the article is written with the actual person who wrote it. When I'm explaining something, I often assume a persona in which I, too, am confused about something. I then give an explanation starting from the same point as those to whom I am explaining. That looks to me like what is being done here. Good pedagogy sometimes involves not being a showoff.
    • Jonathan Gennick photo Learning is nothing to be scared of
      2002-10-03 08:09:16  Jonathan Gennick | O'Reilly AuthorO'Reilly Blogger [View]

      I think you are confusing the persona in which the article is written with the actual person who wrote it.

      Thanks. I appreciate the support. However, the article is substantively correct. I wasn't at all confused about what a join is, but I was indeed surprised by the result of moving what I took to be a non-join condition from the WHERE clause into the FROM clause of a query that was doing an outer-join.

      To address the first poster, I don't see why anyone should find it "scary" that I managed to learn something new that I didn't know before. Just because I edit and write database books doesn't make me omniscient. And it would be utterly foolish for me to stop learning just because I'm an editor. For that matter, I'm actually learning a lot this week: I'm in San Francisco attending a Hotsos Clinic (about Oracle tuning) put on by Cary Millsap.

      The scary part, for me at least, was to write the article in a way that conveyed my initial ignorance, and then my subseqent enlightenment. I could have written the article such that I appeared to know all along what I was talking about. Instead, I shared my learning experience just as it really happened.
      • Learning is nothing to be scared of
        2002-10-03 13:39:49  Dave Rolsky | O'Reilly Author [View]

        But it still reflects a lack of knowledge about relational theory that is a bit unsettling to me.

        I think the key quote is this:

        I had thought that the use of the ON clause versus the WHERE clause was mere eye-candy, and that all conditions were treated identically no matter where they were placed in the query.

        Well, if you only know Oracle and SQL, that's pretty much what I'd expect. But you _should_ know more than that, shouldn't you?

        SQL (at least the version used by Oracle) obscures the difference between join and non-join conditions, but you should have known that already.

        And yes, learning is good, no matter what your position, but I'd still expect someone who writes and edits books about databases to know better.