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• T-SQL Tuesday #13: Clarifying Requirements

  When we transform initial ideas into clear requirements for databases, we typically have to make the following choices: Frequent maintenance vs doing it once. As we are clarifying the requirements, we need to determine whether we want to concinue spending Read More... Posted Monday, December 13, 2010 9:26 PM by Alexander Kuznetsov | 0 Comments Filed under: query performance, query tuning

• Yet another example of defensive query optimization

  My second take at the same problem I blogged about yesterday: To optimize a query, we frequently have to explicitly tell optimizer some information which it does not realize by itself. Short term, this works, but long term we run the risk that what we Read More... Posted Thursday, February 18, 2010 3:11 PM by Alexander Kuznetsov | 1 Comments Filed under: Defensive programming, query performance, Transact SQL

• Optimizing yet another query that involves highly correlated columns

  In some cases some of the columns involved in a query are highly correlated. If you manage to communicate to the optimizer that valuable information, it may come up with a more efficient plan. For example, consider the following table (the script that Read More... Posted Monday, July 13, 2009 6:15 PM by Alexander Kuznetsov | 2 Comments Filed under: query performance, Transact SQL

• Using CROSS APPLY to optimize joins on BETWEEN conditions

  Recently I encountered a case when I knew much more about the data than the optimizer. Originally the performance was horrible, this is why I had to have a look at the query in the first place. When I was able to share my knowledge with the optimizer, Read More... Posted Tuesday, July 07, 2009 8:47 PM by Alexander Kuznetsov | 19 Comments Filed under: query performance, SQL Server

• Override the optimizer or give it an easy task?

  When your query must always return in a certain amount of time, trusting the optimizer might not be the best choice. Suppose your select must return in one second no matter what, and it usually returns in 50 ms, but sometimes, once in 100K calls, it takes Read More... Posted Tuesday, June 16, 2009 10:43 PM by Alexander Kuznetsov | 6 Comments Filed under: Index Covering, query performance, SQL

• Be ready to drop your indexed view.

  In all-too-many cases an indexed view may solve your short term performance goals but at some later time become counterproductive. So if you choose to use an indexed view, you may need an exit strategy. Let me describe a few common problems with indexed Read More... Posted Tuesday, June 02, 2009 5:10 PM by Alexander Kuznetsov | 10 Comments Filed under: Deadlocks, indexed view, lock contention, query performance, Transact SQL