What's in a Condition?
Subject:   Learning is nothing to be scared of
Date:   2002-10-03 08:09:16
From:   gennick
Response to: This is a bit scary ...

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.

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  • 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.