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What You Can (and Can’t) Do With Indexed Views

Last Updated May 9, 2019

Views are logical objects in SQL Server databases that present you with a “virtual table”. Views are typically created for one of three reasons: security, simplification, or aggregation. Security: we create views so that a user can read specific columns out of certain tables, but not all the data. Simplification: sometimes, it’s easier to write…

Filtered Indexes and Dynamic SQL

Last Updated February 13, 2017

Jeremiah Peschka

Indexing, SQL Server

I’ve been told that an attendee at the PASS Summit pre-conference event asked about using dynamic SQL to get around some of the problems with filtered indexes. I’m not entirely sure what the question was, but it did give me the opportunity to play around with filtered indexes and write some simple demo code to…

What You Can (and Can’t) Do With Filtered Indexes

Last Updated January 21, 2019

Brent Ozar Unlimited Team

Indexing, SQL Server

Filters aren’t just for instagram photos. When you write a query, you (usually) don’t want to return all the rows from the table(s) involved – so you add a WHERE clause to the statement. This ensures that fewer rows are returned to the client – but doesn’t reduce the amount of I/O done to get…

Index Hints: Helpful or Harmful?

Last Updated February 13, 2017

Jes Schultz

Indexing, SQL Server

Let me ask you a question: do you want to boss the SQL Server query optimizer around? If you answered no: good. You’re willing to let the query optimizer do its job, which is to find the least expensive way to run a query, as quickly as possible. If you answered yes: you’re a brave…

How Much is Offline During an Index Rebuild?

Last Updated February 16, 2017

Kendra Little

Index Maintenance

Kendra with her Not-A-SAN This question came up in the pre-show chat for our weekly webcast: when you rebuild a nonclustered index offline, does it impact only the nonclustered index? Or does it impact the entire table? Showing is more fun than telling! Let’s take a look. First I restore AdventureWorks to slow storage Sometimes…

Why Index Fragmentation Doesn’t Matter [Video]

Last Updated February 13, 2017

Brent Ozar

Index Maintenance, SQL Server, Videos

Are you still rebuilding all of your indexes every week – or heaven forbid, every night – and still having performance problems? Odds are, you’re not actually making things better – you’re making them worse! I explain why in this video: For more, read my post: Stop Worrying About Index Fragmentation.

Rebuild or Reorganize: SQL Server Index Maintenance

Last Updated February 13, 2017

Kendra Little

Index Maintenance, SQL Server

108

Index maintenance compacts a structure *and* changes physical order– both can be important! Editors Note: this post was updated in June 2014 to link to an online index rebuild bug that can cause corruption. Once up on a time, there was a database server with 500GB of data and a heavy read workload of dynamic…

Trivial Optimization and Missing Indexes in SQL Server

Last Updated May 12, 2019

Kendra Little

Indexing, SQL Server

Recently, Jes asked the team an index tuning question: “If a query has an index hint in it, will the optimizer ever suggest a missing index for that query?” I immediately loved the question because I’d never really thought about it before. I typically think of index hints as being a very risky game and…

How to Find ‘Secret Columns’ in Nonclustered Indexes

Last Updated November 16, 2017

Kendra Little

Indexing, sp_BlitzIndex

sp_BlitzIndex® just can’t keep a secret. That’s a feature, not a bug. I wrote sp_BlitzIndex® specifically so that it would rat out some things that SQL Server is doing behind the scenes to secretly help you out– because it’s really better if you know about it. What are secret columns? SQL Server needs a unique…

The Index Your Queries will Never Request (A Clustered Index!)

Last Updated April 10, 2017

Kendra Little

Indexing, SQL Server

When it comes to indexes, SQL Server is really helpful. It lets you see what indexes queries are asking for both in execution plans, and missing index dynamic management views (“DMVs”). I like to look at the DMV missing index requests using sp_BlitzIndex®. When you look at missing index requests, it’s always important to remember…

Indexing Wide Keys in SQL Server

Last Updated February 13, 2017

Kendra Little

Indexing, SQL Server

Key length matters in SQL Server indexes. It’s a best practice to keep your index keys as narrow as possible, and SQL Server enforces a maximum key length of 900 bytes on most “normal” clustered and nonclustered indexes. But what happens if you want to optimize the lookup of a wide column? You’re not necessarily…

5 Things About Fillfactor

Last Updated February 13, 2017

Kendra Little

Index Maintenance

Are you a page half full, or a page half empty kind of person? I’ll never think “I’ve seen it all” when it comes to SQL Server– there’s just always someone waiting around the corner who’s found a weird new thing to do with it. But there are some things I really wish I could…

What’s Better: Disabling vs. Dropping Indexes?

Last Updated April 2, 2021

Jes Schultz

Indexing, SQL Server

In order to improve your applications and your databases, they will need to change over time. The structure of the database changes, the structure of the tables change, the data in the tables change, the application changes, the queries against the data change. Indexes that once helped performance now just bloat your database and cause extra work…

Best Practices + Table Partitioning: Merging Boundary Points

Last Updated February 13, 2017

Kendra Little

Partitioning, SQL Server

One of the many best practices for SQL Server’s table partitioning feature is to create “extra” empty partitions around your data. This is explained in SQL Server Books Online in the page on altering a Partition Function: Always keep empty partitions at both ends of the partition range to guarantee that the partition split (before…

SQL Server Table Partitioning Tutorial: Videos and Scripts

Last Updated December 29, 2021

Kendra Little

Partitioning, SQL Server, Videos

There’s a secret to learning about SQL Server’s table partitioning feature: you need to get your hands on some code and really play with it in a test environment. In this tutorial, Kendra will walk you through test scripts that set up a sample table partitioning environment. These scripts demonstrate gotchas to look out for…

Potential Problems with Partitioning

Last Updated February 13, 2017

Jeremiah Peschka

Partitioning, SQL Server

Getting started with table partitioning is difficult; there are many decisions to make after you’ve decided to partition data. Correctly configuring partitioning is critical to the long term performance and stability of the database from both a querying and data modification standpoint. There are three key considerations that database architects should devote time to before…

Stop Worrying About SQL Server Fragmentation

Last Updated March 5, 2017

Brent Ozar

Index Maintenance, SQL Server

138

I bet you’re worried about your index fragmentation. If your database was a phone book, it would look like this one. And I bet you’re wasting your time, missing the real point. What is Index Fragmentation and How It Happens Let’s take a step back for a second and pretend that your database is a…

SQL Server Index Terms

Last Updated February 13, 2017

Jes Schultz

Indexing

Let’s have a chat about your indexes in SQL Server. Indexes can be confusing. They are the easiest way to boost performance of queries, but there are so many options and terms around indexes that it can be hard to keep track of them. Let’s chat about the differences between clustered and nonclustered indexes, key…

Hash Partitioning, SQL Server, and Scaling Writes

Last Updated September 2, 2019

Jeremiah Peschka

Architecture, Partitioning

At first glance, SQL Server’s partitioning seems like it should be an easy way to solve problems inserting data into busy tables. If the writes are spread across many partitions it only makes sense that we can avoid write hot spots in SQL Server, right? The truth is much more complicated than it appears. Asking…

How To Decide if You Should Use Table Partitioning

Last Updated October 7, 2020

Kendra Little

Partitioning, SQL Server

153

Great volumes have been written about table partitioning. It’s a complex feature and you can read for days to just understand how you might apply it. But will it improve performance for you? Table partitioning produces great benefits for some applications, but causes giant headaches for others. How do you know if you should invest your…

Indexing

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