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Interviewing a DBA

I’m not a fan of trivia style interview questions. Yes, I ask a few because you have to in order to immediately eliminate the completely unqualified applicants. Even those types of questions, in my opinion, need to be focused on concepts and not syntax. The reason we have the Books Online with SQL Server is because you shouldn’t have to memorize every possible command along with all their parameters. Want to know how to write a MERGE query? Look it up. What does a MERGE query do? That you ought to know. I think concepts are important. Questions about the recovery models within SQL Server aren’t trivia about the system, they’re trying to get to your understanding of how point in time recovery works.

I don’t really like posting interview questions. And most of the time when I’ve seen interview questions posted (even mine), they’re pretty trivial stuff that doesn’t really get to whether or not the person you’re trying to hire is a good fit for the position and your team. I also don’t like posting interview questions because some people will try to use them to study up and attempt to BS their way into a position they frankly don’t deserve and haven’t earned. SQL Server knowledge and experience comes from using it to solve problems out in the world and protecting the information generated by a business.

That’s why I love this question. And I don’t mind sharing it with you because you can’t really memorize an answer to it:

You get a call from one of the business people. They tell you that the database is running slow. What do you do?

This is completely and utterly open-ended. It can go anywhere. In fact, it’s going to go where you lead it. For example, you could say “I first look at the Windows server error logs.” OK, that’s fine (several people I’ve interviewed started there). What indications would you find there that the server is running slow or what would you find there to show why the server is running slow? Suddenly, maybe you don’t want to look at the error logs for the server any more, or maybe you do. But you get the idea. There is no single correct answer here. There are however, lots of very problematic paths, and I’m going to let you go down them. I had one guy insisting that the very first thing he needed to do after the phone call was take a look at the application code to see the method used to make the call to the database. We spent quite a bit of time exploring why this seemed to be the best approach to him. Was it? I’m not saying. No hints on this one. Your answer for this question, is your answer, and that’s why I love it.

Further, as we explore this question, and I’ve spent anywhere from 10 minutes up to an hour working on it as part of an interview, I’m also getting to see how you deal with problematic situations, what your logic chain looks like, what your understanding of SQL Server is, and, most importantly, how you fit into the team. Because with an open-ended question like this, we get to talk. We’re way beyond silly trivia contests now.

Before you think this is unfair to people who aren’t performance experts, fine, let’s talk about what happens when you get an alert that the server is offline. Not a systems person? OK, we just got an alert that a database consistency check failed, now what? See, the point is to go on an adventure where we explore your knowledge and approach. I just have to work hard to make sure we stay somewhat on topic so that I can assess your knowledge and skill level.

Now, if I approach any of these questions and your response is to reject them out of hand, something I’ve run into, then we’re done. I’m not going to focus on trivia, which is how lots of people prep for interviews. I expect you to have concepts, process, logic, and methods available from your time studying and learning. So if we interview, be ready for this exploration, not a trivia contest. And the only way to really prepare is to get experience and knowledge by actually working with SQL Server.

Oh, and sometimes, I ask questions or make statements that are wrong. Sometimes it’s on purpose. Other times, it’s because I screwed up or was ignorant. But you can’t sit there agreeing with me. You better be paying attention because I might be testing you further.

This type of question is just too perfect for understanding how much you know about SQL Server.

Want to start to prepare for answering this kind of question? I’ve got an opportunity for you. At the PASS Summit 2012 this year, I’ll be running an all-day pre-conference seminar called Query Performance Tuning: Start to Finish. In it, I’ll cover quite a bit of what might make it possible for you to answer this question should you be presented it in an interview. No, I’m not guaranteeing you’ll answer it correctly. I’m just offering a chance to prepare. Sign up for the Summit today. There’s still a discount in place that can help you offset the cost of the seminar until the 30th of September.

The Scary DBA

I have twenty+ years experience in IT. That time was spent in technical support, development and database administration. I work forRed Gate Software as a Product Evangelist. I write articles for publication at SQL Server Central, Simple-Talk, PASS Book Reviews and SQL Server Standard. I have published two books, ”Understanding SQL Server Execution Plans” and “SQL Server 2008 Query Performance Tuning Distilled.” I’m one of the founding officers of the Southern New England SQL Server Users Group and its current president. I also work on part-time, short-term, off-site consulting contracts. In 2009 and 2010 I was awarded as a Microsoft SQL Server MVP. In the past I’ve been called rough, intimidating and scary. To which I usually reply, “Good.” You can contact me through grant -at- scarydba dot kom (unobfuscate as necessary).


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