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It’s a Lock: Due Diligence, Schema Changes, and You

Last Updated February 13, 2017

It’s morning standup, and someone says, “It’s no big deal, we just need to add a couple of columns. It’s already in the build, it works fine.” The next time this happens, stop and say, “Let’s take a closer look at that.” When you write schema changes for a relational database, take the time to…

Sargability: Why %string% Is Slow

Last Updated December 29, 2017

Brent Ozar

T-SQL

People love to search. Google has us addicted to fast, easy search functions. Users expect every application to have a built-in blazing-fast search functionality. To pull that off, developers build search queries that let users enter a string, and we ask SQL Server to find matches. For example, say our users need to find some…

Why Use Schemas?

Last Updated February 14, 2017

Brent Ozar

Development

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The ever-insightful Buck Woody (Blog – @BuckWoody) wrote a post telling you to use database schemas. He writes: “But I still see a lot of applications, developed by shops I know as well as vendors, that don’t make use of a Schema. Everything is piled under dbo…. But if you’ll use them properly you can…

Tuning SQL Server Transactions – and Meetings

Last Updated February 13, 2017

Brent Ozar

Locking, Blocking, and Isolation Levels

Meetings are like bad blocking queries – they tie up precious resources and stop other people from getting work done. Today, let’s talk about how to optimize both of ’em by doing homework ahead of time and minimizing the number of objects in the transaction.

Simon Sabin’s talk on query performance

Last Updated March 10, 2021

Brent Ozar

Execution Plans

At #SQLbits, Simon Sabin (Twitter) talked about car crash queries: queries that suddenly have bad performance out of nowhere, yet if you copy/paste them into SQL Server Management Studio, they run quickly. The culprit is often parameter sniffing: the engine looks at the query and builds a plan, but if the parameters in the WHERE…

Book Review: SQL Server 2008 Query Performance Tuning Distilled

Last Updated February 13, 2017

Brent Ozar

Book Reviews, Execution Plans

My gauge of an amazing book is simple: if I’ve got a question, and I reach for the book BEFORE I search the web, then it’s an amazing book. Several times in the last two weeks, I reached for this book first.

Getting Help With A Slow Query

Last Updated October 21, 2017

Brent Ozar

Execution Plans

StackOverflow users often ask, “I’ve got this query that runs slow – can you help?” Here’s a few tips to get better, faster answers, including getting the execution plan and relevant Perfmon data.

SQL Server load testing: synchronized tests versus random ones

Last Updated February 14, 2017

Brent Ozar

Load Testing

Our QA department uses Mercury TestDirector to do load testing of our .NET web apps. The basic idea is that TestDirector runs through a set of URLs to load test an application, and it can gradually scale up the number of simultaneous sessions until the datacenter is filled with smoke. When the fire alarms go…

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