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As some of you might know, I have been to SQLRally Nordic 2012 in Copenhagen earlier this week. I was able to attend many interesting sessions, I had a great time catching up with old friends and meeting new people, and I was allowed to present a session Read More...
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Scalar user-defined functions are bad for performance. I already showed that for T-SQL scalar user-defined functions without and with data access, and for most CLR scalar user-defined functions without data access , and in this blog post I will show that Read More...
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I showed why T-SQL scalar user-defined functions are bad for performance in two previous posts. In this post, I will show that CLR scalar user-defined functions are bad as well (though not always quite as bad as T-SQL scalar user-defined functions). I Read More...
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In a previous blog post , I demonstrated just how much you can hurt your performance by encapsulating expressions and computations in a user-defined function (UDF). I focused on scalar functions that didn’t include any data access. In this post, I will Read More...
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So you thought that encapsulating code in user-defined functions for easy reuse is a good idea? Think again! SQL Server supports three types of user-defined functions. Only one of them qualifies as good. The other two – well, the title says it all, doesn’t Read More...
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The optimizer is the part of SQL Server that takes your query and reorders and rearranges your query to find the optimal execution plan. In theory. In practice, that doesn’t always work out well. Often, the optimizer manages to come up with brilliant Read More...
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Almost two months have passed since my last blog post. And while it’s true that I’ve had (much) longer breaks, I do have a good reason now. All the time that I would normally at least in part spend on preparing new blog posts is now reserved for preparing Read More...
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I guess that many people using UPDATE … FROM on a daily basis do so without being aware that they are violating all SQL standards. All versions of the ANSI SQL standard that I checked agree that an UPDATE statement has three clauses – the UPDATE clause, Read More...
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Did you know that SQL Server allows stored procedures to have up to 2100 parameters? And more important: do you care? Well, some people do care, and Joe Celko seems to be one of them. If you are a regular reader of SQL Server newsgroups, you probably Read More...
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In this fourth and final part in my series about NULL, I’ll discuss some well-known and some less well-known functions and keywords that are specifically created to deal with NULL values. And I will, of course, explain why null if null is null null null Read More...
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Two months ago, I posted the first two parts of a series about NULL. After that, I went quiet. Much to do and little time was one excuse. But to be honest, I also lost interest. However, I felt I owe my readers to conclude the series, so I have now forced Read More...
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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 Read More...
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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, Read More...
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On December 31 of last year, I posted this brain teaser , promising to post the answer “in a few days”. Apparently, 15 is a few J . In case you have forgotten what the puzzle was about and are too lazy to click the link above, the bottom line is that Read More...
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Here’s a nice brain teaser, just before the end of the year. Despite the title, it is related to SQL Server, not to music! A common misconception amongst SQL Server users is that a clustered index on a table will ensure that data is returned in the order Read More...
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