<snip> > > I agree with most everything you said, as far as the use of a RDBMS, and > especially: quoting you, > > "theoretically you break up your data into tables so that there is never a > non-applicable field for any given row." > > Here is where I disagree with you, and please DON'T take this as an insult > (we're just haggling over good/bad practices ),
No Insult or offense taken. Sorry for opening this can of worms ;) > but I think it is lazy > database design when you say: > > "In the real world, this can lead to a lot of complexity, so many people > usually cheat and have a few "does not apply" fields for some records." > > OK! Now here is my top 5 explanations why using Nulls is a bad idea: > > Explanation(5): The more you understand how the database is to be used, > and the more complexity and thought you put into your database design, the > less complex it will be to retrieve reliable information out of it. > Furthermore, (and this is probably what makes me crazy when Nulls are > evolved) after a ten year stretch of software development, where I and a > team designed our own databases, I did a nine year stretch of statistical > programming, using databases designed by other people, and Nulls in the > data made the results unpredictable, and yeah, made me crazy! I had to > write nightly processes to resolve inconsistencies in the data, if at > least report inconsistencies. You know the old saying "Garbage in = > Garbage out", to me Nulls are garbage, and if there is a good reason for > nulls to be a part of good clean data then someone please help me > understand that. > > Explanation(4):I think that the brilliant computer scientists who > developed the RDBMS database model, didn't want to support nulls > initially, but they had to because null is a form of data, it means "We > don't know what this is", and so it must be stored knowing that Null > should NOT be used as valid information. > > Explanation(3):I think it was back in the sixties at Berkley, when some > smart guy on LSD found a use for the Null value, and now this use of Null > is taught in Universities all over the world, and considered to be a > blessed method to practice. > > Explanation(2): Using a Null column, and you have an index on that column, > the index will not be used since NULL values do not get stored in an index > and that is why the optimizer will need to go to the data pages in order > to retrieve more information to suffice the requirements of the query. > > Explanation(1): I'm just in a argumentative mood today. > I'm staying out of the debate on numbers 3,4 and 5, but I am watching with interest. Number 2 is very good to know and I will make note of that. as for number 1, well ...? > Cheers and have a great weekend! > Mike. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
