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Definitely didn't mean to imply that you personally don't understand NULLs
Joe. I've seen and read enough of your content to know that you have a very
good handle on impressive variety of technical concepts. I doubt anything I
write will be news to you.

I try to write for a general audience instead, based on what my experience
is of the RLA demographic. Since it's based on my experience, it's
obviously biased. Even though my comments don't apply to you, I still stand
behind them. I can only hope they help some of the listers reading them but
decide not to post (silent majority?).

As for COALESCE, in that particular scenario I thought it could be ambiguous
(i.e. did the join really come back with a 0, or was that as a result of a
COALESCE default). Perhaps it doesn't matter. I don't have anything
against the COALESCE itself.

As for Codd & Date, if I had to, I would probably read Codd, again due to a
personal bias (my database professor met him, based a lot of his work on
Codd's theories while working at IBM and agreed with most of his ideas [but
not all]).

Elvis

Celebrating 11-Years of SQL Performance Excellence on IBM i, i5/OS and
OS/400
www.centerfieldtechnology.com


-----Original Message-----
Subject: Re: Interesting question and debate on ddl tables withdate
fieldsthat will not always have a value

Elvis Budimlic wrote:
Understanding and use of a NULL concept is required when using SQL.
If I create a LEFT OUTER JOIN sql query, project some columns from the
secondary dial and some of the join conditions have no match in the
secondary dial, the result set will include NULLs even though the tables
being joined have no NULL capable fields. If this query is in embedded
SQL, the developer has to handle this case.

Nobody said anything about not understanding NULL. We were talking
about using NULL to store values in the database.

Traditional RLA developer may handle it by forcing the secondary dial
projections to a non-NULL field using COALESCE, but that is not the best
way to handle it. Using null indicators is.

What have you got against COALESCE? They certainly didn't add it to the
language for RPG programmers <smile>.

Again, if no SQL access is used, value of understanding and use of NULL
diminishes, although it doesn't disappear.

Another reason I hate these discussions. Because I don't like NULLs,
that means I don't understand them or SQL. Oh pshaw, Elvis <grin>.

What I think has not been mentioned yet in this thread is that most of the
other database platforms use SQL exclusively to access the database, so
developing understanding of these types of concepts could benefit
developers whose retirement is not just around the corner by making them
more versatile and marketable. Or simply able to help their non-i
development team.

Please review my posts on the subject and find one place where I
suggested that programmers should not understand NULL. On the contrary,
I think programmers SHOULD understand NULL - that way they'll be more
likely to use them appropriately. I think you yourself, Elvis, might
benefit from reading Chris Date and Dr. Codd's writings on the subject
to understand their views, which differ from your own.

This, though, is why I hate these threads. Because I don't like
something means that I don't understand it. If you knew me, you'd know
that's usually the opposite of the case; I don't form an opinion one way
or the other about a topic until I understand it pretty well.

I use SQL every single day. I find it indispensable for analyzing data
relationships, for finding anomalies in real world data, and for
providing quick answers to data-related questions. Still, I still find
that business logic is better represented in RPG than in SQL, and I find
RLA to be easier to write, document, and extend. But if you go back
through this list, you'll find that I'm one of the top posters when it
comes to answering SQL questions. So I'd say you would be wrong to
imply that I don't understand SQL because I don't like NULLs.

Enough for this morning... off to work...

Joe



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