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I received a question from a friend in Brazil related to foreign keys and join elimination in SQL Server. Yes, SQL Server can detect that some joins are not needed to return results to the user and skip them. What is this evil magic, you ask?
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(Not a SQL Server post) I have been meaning to install Windows 7, and I got around to doing it last night. I usually run Windows 2003/8 Server for work, so my interest in the consumer side is perhaps not as high as some others. Nevertheless,
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I gave a talk to the Austin-area PASS group last night on B-Tree indexing in SQL Server, and I received a question about whether to make clustered indexes UNIQUE or not (assuming the data is unique on the key columns). The expectation was that this
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As most of you have figured out by now, I work mostly on queries :). One of the things that I often need to do is to get a statement out of a batch so that I can go look more closely at a query plan (and, in my case, the code that generates it).
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My coworker Marc posted up a good introduction into the different server cursor models and you can see it here: http://blogs.msdn.com/sqlqueryprocessing/archive/2009/08/12/understanding-sql-server-fast-forward-server-cursors.aspx
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It’s been a busy summer. I got back from vacation and have been hard at work on new features for a future version of SQL Server. You can always still send me questions about the existing product, of course, and I will answer them here (conorc
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I received a question from a customer today about query plan choice for a parameterized query - specifically that different plans get picked based on where the plan is located, and sometimes one might be better than another. Apparently, for their
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Thanks to those of you who replied to my previous post. I spent the last week or so talking with customers, coworkers, and looking at various applications to see how recompiles are modeled today in their applications. At a high level, SQL
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I have a question for you guys about how do you force a recompile for a single query today? There are a lots of different ways that one could cause the system to recompile a query: a) sp_recompile <object used in a query> b)DBCC FREEPROCCACHE
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I received a question this week about whether filtered statistics update as frequently as regular statistics. The right way to ask the question is “Do filtered statistics become invalid as frequently as regular statistics?”, as stats are recomputed
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For those of you waiting for the new "Inside SQL Server" book, it is actually out now. Kalen decided to give it a name change, and the actual title is "SQL Server 2008 Internals". I've written a chapter on how the Query
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A customer recently asked our support organization about an unexplained series of range locks that they were seeing on a DELETE to a table with a foreign key. Here is the repro: 1: create table Foo (FooId int not null primary key ) 2: create table
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(as ANSI NULLs is one of the requirements for indexed views, I thought I’d give you some perspective on why the questions I ask you are useful and interesting to better understand queries and various query operations) As currently designed, indexed
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I was thinking about indexed views. Well, more specifically, I was thinking about why indexed views are hard to use. One of the reasons that they are hard is that there are just so many restrictions. Anyways, one of the things I'd like to better understand
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MERGE is a new operation added in SQL Server 2008. It has all sorts of knobs, bells, and whistles. The primary value of this feature is to collapse multiple query statements into one query statement. Overall, this avoids the “overhead” necessary to run
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