Clustered vs. Nonclustered Index Structures in SQL Server

Clustered and nonclustered indexes share many of the same internal structures, but they're fundamentally different in nature. Watch Microsoft Certified IT Professional Jon Seigel explain the similarities and differences of clustered and nonclustered indexes, using a real-world example to show how these structures work to improve the performance of SQL queries.

Blog post on primary key vs. the clustered index:

CREATE INDEX statement reference:

ALTER INDEX statement reference:

Index navigation internals by example:

Sample index data is from the AdventureWorksLT2008R2 sample database:

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[nonam]

No nonsense talk or waste of time.
Straight to the point with excellent presentation examples.
Good Work. Thank you very much.

[abhiramm]

It is hard to believe that this video is from 8 years ago. Still the best video explaining the basics of both these indexes even in 2022.

[falxonPSN]

This is one of the best videos on this topic out there. Keeps it simple, but still clearly explains the structures and how it works. Very nice work, sir!

[sharaf]

Never before did Nicolas cage explain something so well, good job Nic.
joking :D it was so helpful. thanks.

[Alstash]

Elegant explanations like this are truly timeless, shifted through a bunch of videos attempting to word this same information in, like, double the time, and yet STILL failed to deliver as well as you did, sir, truly thank you.

[lorraineliu]

I've watched over 10 video. This is by far the most clear structured introduction to indexes! Thank you!

[xphon]

Great explanation! This is the type of explanation that every developer can understand, no matter their programming level

[CorbinBohne]

I always come back to this video when I need a refresher and it never fails to help me. Thanks again!

[edwardsun]

Man,   you fully rocked on demonstration the difference between Clustered Index and non-clustered Index !    This helps me on preparing for the interview questions !

[radekou]

Wow, great explanation, love the usage of visualization of the data stored in structures. I've had an idea about how indexes work, but after watching this I'd be able to explain it to my grandmother (:

[davewhelton]

For 10 years, I've learned the definitions of both coz i just couldnt grasp what it actually meant but the 2nd time watching this video, you have finally made me understand

[kzev]

You are awesome. Without ppl like you I would not have been able to build my skill at this level and get the job I now have. It all goes far. Thank you very much!

[nkproductions]

Incredibly beautiful explanation of clustered and non-clustered indexes. There is a lot of material in those first 6 minutes, and I admit I had to pause several times to absorb it and move, but hey who is complaining when you get there eventually.

[samlinus]

Man, you've researched a lot such a quality video, you just kept answering all of the questions that I had referencing blogs and videos. God bless you brother

[michaelgebreselassie]

I have been looking for different sources just to objectively understand the difference between clustered and non-clustered indexes and to know how they really work. This very short and precise video have put an end to all of my Qs. Thank you.

[georgesmith]

I liked the visualizations best. The phrase "a picture is worth a thousand words" definitely applies to this video.
Thanks for the concise and well delivered video. And, please, ignore the "Nicolas Cage" references below.

[kezhan]

Wow, I could not image a man can explain it in such a simple way! Thank you!

[MegaSmsm]

the best tutorial i have ever seen for MS SQL indexes, good job my friend

[camelCased]

Thanks for the video, the phonebook example was good and easy to understand.
From my experience, things sometimes get confusing because of different default behavior of different RDBMS - some automatically create clustered indexes for primary keys, some automatically create indexes on foreign keys, and some don't do any of this. So, sometimes you might get unpleasant surprises and performance issues if you have to deal with a RDBMS which you don't have experience with.

[tehawesmesauce]

This video might save my advanced databases test grade tomorrow. I hate when the prof. doesn't explain stuff clearly enough for me. Thanks for the video - liked and subbed! :)