Month: July 2007

A Better Developer in 6 months? Deal!

It’s all the fault of Denis Gobo. He tagged me, and now I feel obliged to publish my plans for the last half of 2007 as well. I am not quite as ambitious as Denis, though.   My first commitment Like Denis, I will read more technical books. I have a huge stack of unread books on my desk, that I will try to finish. Here are the books, in planned reading order: Inside Microsoft SQL Server 2005: T-SQL Programming, by Itzik Ben-Gan. A Developer’s Guide to SQL Server 2005, by Bob Beachemin and Dan Sullivan. MCITP Self-Paced Training Kit…

The logic of three-valued logic

In my previous post, I explained what NULL does and does not mean, how and why the rule of NULL propagation forces any expression involving NULL to result in NULL. I also mentioned that comparisons involving NULL do not result in NULL but, rather, in a new “truth value” called “Unknown”. But there’s a lot more to be written about Unknown and it’s effect on logical expressions, and that’s exactly what this blog post (and the next one as well) will be about.   Most software developers will be intimately familiar with what is popularly known as Boolean logic but…

NULL – The database’s black hole

I once read a scientific article on black holes that started of on the observation that, since a hole is the absence of anything and black is invisible in space, a black hole is in fact an invisible nothing – so what the heck are we talking about? Well, almost the same can be said about NULL in databases.   Let’s first take a look at what NULL is supposed to be. Here is the definition of NULL from the SQL-2003 standard:               null value: A special value that is used to indicate the absence of any data value.…

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