SQLServerFast

Upcoming speaking engagements – want to meet me?

Hugo Kornelis
No Comments
I have a very busy time ahead of me, with lots of travel, lots of speaking engagements, and hence lots of opportunity to meet and catch up with what has become known as the SQL Family. (An excellent term, by the way – it describes exactly how it has always felt to me!) So, for everyone who want to know when and where they can meet me (as well as for everyone who wants to make sure to stay as far away from me as possible), here is my schedule for the rest of the year, in chronological order: ·…
Read More

T-SQL User-Defined Functions: the good, the bad, and the ugly (part 3)

Hugo Kornelis
8 Comments
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 will admit that I had not really planned to cover CLR in this series. But shortly after publishing the first part, I received an email from Adam Machanic, which basically said that I should make clear that the information in that post does not apply to CLR functions. So I dutifully added a comment to that post, and…
Read More

T-SQL User-Defined Functions: the good, the bad, and the ugly (part 2)

Hugo Kornelis
1 Comment
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 complete the discussion on scalar UDFs by covering the effect of data access in a scalar UDF. Note that, like the previous post, this all applies to T-SQL user-defined functions only. SQL Server also supports CLR user-defined functions (written in a .Net language like C# or VB.Net); those are not in the scope of this blog post. Data access…
Read More

T-SQL User-Defined Functions: the good, the bad, and the ugly (part 1)

Hugo Kornelis
39 Comments
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 it? The bad: scalar functions A scalar user-defined function (UDF) is very much like a stored procedure, except that it always returns a single value of a predefined data type – and because of that property, it isn’t invoked with an EXECUTE statement, but embedded in an expression where the returned value is immediately used. I…
Read More

Principles of Modeling: Avoid Redundancy

Hugo Kornelis
1 Comment
In 1994, I learned a method for data modeling that is based on three principles. I immediately knew that these principles should embraced by anyone who does any data modeling or process modeling. Or almost any other job, for that matter. I have described these principles in three previous blog posts: the Jargon Principle, the Concreteness Principle, and the Reproducibility Principle. But I have later found that there are more principles and guidelines that are important to keep in mind when modeling. Avoid Redundancy I almost hear you think: “Yes, avoid redundancy. Duh! Do you have any more open doors…
Read More

The Curious Case of the Optimizer that doesn’t

Hugo Kornelis
7 Comments
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 ways to execute a complex query very efficiently – but sometimes, it misses an option that appears to be so simple that you can only stare in utter amazement at the execution plan before going to the Connect site. Here is an example I recently ran into. I tested it on SQL Server 2012 and on SQL…
Read More

Slides and demo code for Columnstore Index session

Hugo Kornelis
1 Comment
Almost a week has passed after SQLBits X in London, so I guess it’s about time for me to share the slides and demo code of my session on columnstore indexes. After all, I promised people I would do that – especially when I found out that I had enough demos prepared to fill two sessions! I made some changes to the demo code. I added extra comments, not only to the demos I could not explain and run during the session, but also to the rest, so that people who missed the session will also be able to benefit.…
Read More

80% off for SQL Azure!

Hugo Kornelis
1 Comment
I have spent the last three days at SQLBits X in London – a truly great experience! There were lots of quality sessions, but I also enjoyed meeting new people and catching up with old friends. One of these friends (and I hope he’s still a friend after I post this) is Buck Woody. Not only a great and humorous speaker, but also a very nice fellow – for those who don’t mind being teased every now and then. When we were chatting, he told me that he was planning to announce a special access code to allow attendees of…
Read More

Busy months ahead

Hugo Kornelis
2 Comments
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 presentations for a few upcoming events. I’ll give you an overview – who knows, maybe you’ll have a chance to attend one of them and meet me there? I’m looking forward to it! On Saturday, February 25, I’ll present my session on “Advanced Indexing” at SQL Saturday 108, in Redmond, WA.…
Read More

Principles of Modeling: the Reproducibility Principle

Hugo Kornelis
3 Comments
A year or so ago, I watched a few episodes of a Dutch television program that had an interesting format. The name of the series was (or is, I have no idea if it still runs) “Sterren op het doek” (“Stars on Canvas”). Every episode featured a Dutch celebrity, three painters, and an interviewer. For the program, the three painters each paint a picture of the celebrity (who is interviewed while posing – and because this takes a long time, the interviews were typically quite deep, and had enough material for an interesting first 15 minutes of the program). After…
Read More

Hugo Kornelis

Married, father of 2 children.

Awarded 13x MVP (2006-2016; 2019-now), in the areas SQL Server and Data Platform.

Subscribe via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Archives

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close