Posts by Brent Ozar

When Do I Need to Use DESC in Indexes?

If I take the Users table from any Stack Overflow database, put an index on Reputation, and write a query to find the top 100 users sorted by reputation, descending: CREATE INDEX Reputation ON dbo.Users (Reputation); SELECT TOP 100 * FROM dbo.Users ORDER BY Reputation DESC; 12345 CREATE INDEX Reputation ON dbo.Users (Reputation); SELECT TOP 100…
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What It Takes To Write Two Blog Posts

This week, I published two blog posts: How Bad Statistics Cause Bad SQL Server Query Performance How Scalar User-Defined Functions Slow Down Queries Let’s talk about the process of writing ’em. A couple I was putting together this week’s First Responder Kit release, I realized sp_BlitzIndex didn’t have URLs for a couple of common families…
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When You’re Troubleshooting Blocking, Look at Query #2, Too.

When I’m troubleshooting a blocking emergency, the culprit is usually the query at the head of a blocking chain. Somebody did something ill-advised like starting a transaction and then locking a whole bunch of tables. But sometimes, the lead blocker isn’t the real problem. It’s query #2. Here’s a sample scenario: A long-running select with…
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How Scalar User-Defined Functions Slow Down Queries

T-SQL
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When your query has a scalar user-defined function in it, SQL Server may not parallelize it and may hide the work that it’s doing in your execution plan. To show it, I’ll run a simple query against the Users table in the Stack Overflow database. SELECT TOP 100 DisplayName, Location, Reputation, Id FROM dbo.Users ORDER…
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Paul White Explains Temp Table Caching 3 Ways

TempDB
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Paul White, Debugger of SQL Server Paul White (Blog, @SQL_Kiwi) is a legendary SQL Server blogger who’s written a ton of good material. You should read all of it. You won’t, and I can say that with authority because…I don’t read it all either. It’s too much. But when your job eventually requires you to…
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Why Full Text’s CONTAINS Queries Are So Slow

SQL Server’s full text search is amazing. Well, it amazes me at least – it has so many cool capabilities: looking for prefixes, words near each other, different verb tenses, and even thesaurus searches. However, that’s not how I see most people using it: I’ve seen so many shops using it for matching specific strings,…
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How to Learn SQL Server in One Year

You’ve been using Microsoft SQL Server for a few years, and it’s becoming increasingly important to your job. You can write a query, but… You feel like something’s missing. You attended a few local user groups or meetups before the quarantines hit, but you were disappointed at how scattered the sessions were. The material was…
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