What a rush. Standing on the stage in an almost-full 1,000-person room, I (very) momentarily wondered what I'd been thinking when I submitted a 500-level talk for the biggest SQL Server conference in the world. But despite a rough start--my laptop crashed and I had to reboot it two minutes into the talk--I found my rhythm and the entire 90 minutes ...

Autumn is creeping inevitably closer here in the US, and that means that speaking season is about to kick into high gear. Here's my current schedule for the remainder of the year:   September 8, 17:00 GMT (online) - 24 Hours of PASS webcast: ''Baseline Basics or: Who Broke the Database?''In this session, excerpted from my PASS Summit ...

Thanks to everyone who took the time out of their conference experience to join Mike Wachal and me for yesterday's session on SQL Server performance tuning! For those who weren't there, we focused in on troubleshooting techniques, highlighting some of the key DMVs and new Extended Events features that will help with proactive diagnosis of ...

Last week at SQL Bits #8 in Brighton, England, SQL Sentry (my employer) announced its partnership with DBSophic, makers of the Qure workload management suite. Qure Workload Optimizer is a tool aimed at analyzing a workload and providing suggestions to improve the overall performance of that workload. These suggestions can range from adding and ...

Almost six years ago--in November of 2004--I posted what would turn out to be one of my most popular blog posts in terms of number of reads, ''Performance: ISNULL vs. COALESCE.'' (If you're curious, the post is dated July 2006 because I was too lazyit was difficult to transition the publication dates over with the posts when I transferred to ...

A few days ago Aaron posted yet another fantastic entry in his Bad Habits series, this one discussing mishandling of date ranges in queries. This is a topic near and dear to me, having had to clean up a lot of poorly thought out code in the past few years. Aaron's post includes many examples, all of which boil down to the proper way to do the job, ...

Since I will be speaking about the Query Optimizer at the coming PASS Summit, I have been preparing my presentation and at the same time blogging about it. This time I will describe the Missing Indexes feature, seen from the point of view of the Query Optimizer.   We know that it is the job of the Query Optimizer to find an efficient ...

  This post shows how the Query Optimizer uses statistics to estimate the selectivity of expressions during query optimization.   You can also use this as a second part of my last post, The Query Optimizer and Parameter Sniffing. Here I will show you the advantage of the use of statistics when the Query Optimizer can “sniff” the ...

  As we all know, the SQL Server Query Optimizer uses statistics to estimate the cardinality and selectivity of predicates of a query to produce an optimal execution plan. The Query Optimizer accomplishes this by first inspecting the values of the query parameters. This behavior is called parameter sniffing and it is a good thing. Getting an ...

In my previous post I talked about contradiction detection as one of the early steps in query optimization. Another interesting step performed during query optimization is the automatic matching of computed columns. Although computed columns have been available in previous versions of SQL Server, the automatic matching feature was introduced until ...