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Category: SQL Performance

Checking if a non-LOB column needs to be updated

Occasionally I see people try to "optimize" their update statements to avoid writing the same value to a particular column. My understanding has always been that if you're going to update a row, assuming all of the values are in-row, the costs of locking the row are much higher than the incremental cost of updating one, two or all columns in that row.

  ◆  October 3, 2012
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Database smarter with deeper insights for Microsoft SQL
Hit-Highlighting in Full-Text Search

Hit-highlighting is a feature that many people wish SQL Server's Full-Text Search would support natively. This is where you can return the entire document (or an excerpt) and point out the words or phrases that helped match that document to the search. Doing so in an efficient and accurate manner is no easy task, as I found out first hand.

  ◆  September 24, 2012
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How much impact can a data type choice have?

I've long been a proponent of choosing the correct data type. I've talked about some examples in a previous "Bad Habits" blog post, but this weekend at SQL Saturday #162 (Cambridge, UK), the topic of using DATETIME by default came up. In a conversation after my T-SQL : Bad Habits and Best Practices presentation, a user stated that they just use DATETIME even if they only need granularity to the minute or day, this way the date/time columns across their enterprise are always the same data type. I suggested that this might be wasteful, and that the consistency might not be worth it, but today I decided to set out to prove my theory.

  ◆  September 13, 2012
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What is the most efficient way to trim time from datetime?

The most common need for stripping time from a datetime value is to get all the rows that represent orders (or visits, or accidents) that occurred on a given day. However, not all of the techniques that are used to do so are efficient or even safe. If you want a safe range query that performs well, use an open-ended range or, for single-day queries on SQL Server 2008 and above, use CONVERT(DATE). Read on to discover why…

  ◆  September 5, 2012
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What is the fastest way to calculate the median?

Medians require sorting. Sorting in SQL Server is typically a pretty expensive operation if there isn't a supporting index, and adding an index to support an operation which probably isn't requested that often may not be worthwhile. This post explores the performance characteristics of several solutions to the median problem.

  ◆  August 29, 2012
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Performance impact of different error handling techniques

People wonder whether they should do their best to prevent exceptions, or just let the system handle them. I've seen several discussions where folks debate whether they should do whatever they can to prevent an exception, because error handling is "expensive." There is no doubt that error handling isn't free, but I would predict that a constraint violation is at least as efficient as checking for a potential violation first. This may be different for a key violation than a static constraint violation, for example, but in this post I'm going to focus on the former.

  ◆  August 22, 2012
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My Perspective : The Top 5 Most Common SQL Server Performance Problems

As lots of you know already, Kevin Kline (blog|@KEKline) has joined us here at SQL Sentry. I’ve followed Kevin myself for a good while, so I’m really excited to have him here with us.

One of the first things Kevin asked of me was to list the top 5 technical issues we see while providing customer service for SQL Sentry. For our Client Services team, technical support is far more than just supporting our own software products or managing licenses. Everyone on the team is deeply trained in SQL Server, Windows and Microsoft .NET. In fact, in general, any member trained on our Client Services team should be able to walk into the role of a Windows sysadmin, SQL Server DBA or .NET Application Developer with very little adjustment effort.

  ◆  August 17, 2012
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