Month: November 2008

A bit like putting your laptop into Flight Mode, I guess. I fly fairly often at the moment, but my Wireless switch on the side of my laptop is slowly wearing out. Occasionally when it’s in the OFF position, it thinks it’s actually in the ON position for a moment, and I see the WiFi LED come on. It’s probably a warranty item which I should get fixed soon. But until I do, I’m in the habit of opening up Computer Manager and disabling the device. So I got to thinking that I should be able to do this with … Continue reading Disable WiFi with PowerShell

Ok, it’s not really a problem with America, just a problem with the perception of straight lines like the USA-Canada border. It’s roughly the latitude line 49 degrees north. A line that goes East-West, on a straight line. Except that latitude lines aren’t straight – except the equator. Just look on a globe and you’ll see what I mean.The curvature of the earth just gets in the way a bit. If you’re ten miles from the North Pole and travel east until you come back on yourself, you’ve just gone around in a circle that’s 20 miles across. The smaller … Continue reading The problem with America – spatial data

When you select data out of a database table, it might seem as if the system will give you data in the order of the clustered index that is on that table (assuming it has one), but this isn’t quite right. I showed this in the fifth of my T-SQL tips at TechEd Australia this year. If you don’t explicitly order data using the ORDER BY clause, the system makes no attempt to provide you with the data in any particular order. It will just give you the data in the fastest way possible. You might be lucky and get … Continue reading Ordered data requires ORDER BY

Indexes are great, but if you don’t understand the significance of unique indexes, then you’re potentially missing out on some decent performance gains. I’ve been meaning to write this blog post for a long time. This is material that I’ve been teaching and presenting about all year, but somehow it’s never turned into a blog post. It was the third tip in my presentation at TechEd Australia (and at user group events in Adelaide and Melbourne). Today I’m flying back home from the US, so hopefully I’ll be able to spend some battery time getting it done. [Note: It’s ended … Continue reading Unique Indexes with GROUP BY

This is another of my tips/techniques that I demonstrated recently. It is not a new SQL Server 2008 feature – it works just fine in older versions – I demonstrated it running on SQL Server 2005 but using SQL Server 2008 Management Studio. [Note: It’s ended up appearing earlier than another post that I wrote on the plane. This one is Tip #4.] When you have a single-table query and then introduce a JOIN, there are a number of ways in which that JOIN impacts your query. I want to talk about four such JOIN effects that I’ve identified. Understanding … Continue reading JOIN simplification in SQL Server