Tech Ed isn’t even over yet, and my new Hekaton Whitepaper is already generating questions I can’t answer yet! Here are the two questions that were in my inbox this morning: 1. The whitepaper says “There are other wait types, such as waiting for a log write to complete.” Does this mean that writing to the transaction log  will be ...

  It’s been over 5 years since I last blogged about trace flags, so it seems a post on the topic is in order. If a trace flag is undocumented, it means it is unsupported and not guaranteed. It can go away at any time, even from one service pack to the next. If a trace flag doesn’t work the way the person who told you about said it should ...

I had a very educational exchange the other day on Twitter (also known as “getting schooled”) by my SQL compatriots Argenis Fernandez (@DBArgenis) and Hugo Kornelis (@Hugo_Kornelis). A guy called Chris Switalski (@crswit) asked a really interesting question on #sqlhelp, which I proceeded to answer incorrectly, which led to a correction by my ...

  When I first began working with SQL Server several years ago, one thing that really hung me up was, not understanding why I could reference an Alias column in certain parts of my query, but not in all parts of my query. To be more specific, why I could reference my Alias column in my Order By clause, but I couldn’t reference the alias in ...

It's an old story you've probably heard before.  Provide a free version of your software product with strict limitations on performance or other specific capabilities so that folks can give it a try without risk, while you minimize the chance of cannibalizing sales of your commercial products.  Microsoft has take this strategy ...

Recently I had to take care of the most interesting corruption case I’ve even seen, so decided to share this experience with you. We’re talking about small accounting program which keeps its data in SQL Server Express – in this particular case in SQL Server 2005. The customer called today and sent me following error screen (nice screenshot – taken ...

I love SQL Server execution plans. It is often easy to spot the cause of a performance problem just by looking at one. The task is considerably easier if the plan includes run-time information (a so-called ‘actual’ execution plan), but even a compiled plan can be very useful. Nevertheless, there are still times where the execution plan does not ...

Version 1.0 is Now Available! I’ve been working off and on, as my real job permits, on this visualization tool for SQL Server data files. This is an educational or exploratory tool where you can more readily see how the individual data pages in MDF/NDF files are organized, where your tables and indexes live, what effect operations like index ...

Enabling compression on your database can save you a lot of space – but when you have a lot of varchar(max) or nvarchar(max) data, you may find the savings to be limited. This is because only data stored on the data and index pages is compressed, and data for the (max) data types is generally stored on other, special-purpose pages – either ...

This is part three of a blog series illustrating a method to render the file structure of a SQL Server database into a graphic visualization. Previous Installments: Part 1 Part 2 Those that have been reading this series might be be thinking, “Is he going to go there?” Well, the answer is “Yes.” This is the GUID clustered index post that had to ...