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:
voluntarydba.com/post/2012/10/...
CREATE INDEX statement reference:
technet.microsoft.com/en-us/li...
ALTER INDEX statement reference:
technet.microsoft.com/en-us/li...
Index navigation internals by example:
sqlblog.com/blogs/paul_white/a...
Sample index data is from the AdventureWorksLT2008R2 sample database:
awlt2008dbscript.codeplex.com/...
Visit my channel for more database administration videos:
/ voluntarydba
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ruclips.net/user/voluntarydba?...
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[@nonam72]

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

[@abhiramm4941]

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.

[@ColonelStraker]

Is it just me or did his eyebrows grow, during the course of this video and its edits?

[@lorraineliu8422]

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

[@edwardsun4079]

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

[@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.

[@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!

[@michaelgebreselassie99]

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.

[@CorbinBohne]

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

[@sharaf515]

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

[@VoluntaryDBA]

+Abd El-Rahman Ibn Omar lol

[@diasneto5231]

kkkkkkkkkkkkkk

[@doumkatekz]

And Nicolas Cage old has an odd sort of hottness. :)

[@diananggriawanh8202]

HahhHahahah XD exactly

[@learningearning8385]

ha!!

[@xphon12]

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

[@vincewon8591]

Thank you so much for posting this! I was having a hard time understanding the differences between the two until i watched the video.

[@jonobaker]

This video helped me ALOT, I've been watching many videos and this really clearly cleaned things up for me. The moving graphics were a big part of that too.
thankyou!

[@nkproductions742]

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.

[@MegaSmsm2011]

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

[@VoluntaryDBA]

Thank you very much! I'm glad it helped you.

[@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 (:

[@ashish7459]

Really amazing, I was not aware that we can define type of index while applying primary key or unique constraints. thanks for amazing explanation :)

[@danm2756]

wow....best explanation. I'm studying for the mcsa exam. I've been struggling with this topic. thanks!!

[@TheGothicSecret]

Thank you for painting and diving deep in details of indexes!

[@amaxamon]

I know this has been up for 6 years but THANK YOU!!!!

[@kezhan01]

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

[@mike_yon]

This has been a great straightforward video that really helped explain the difference. Thank you keep up the good work!

[@jacksrensen4475]

Very good explanation ;) My tutors have tried to explain clustering and indexing for me multiple times, without my understanding. But your examples and explanation of the differences really helped

[@mikedaniels755]

Perfectly concise and to the point. Well articulated and the visualizations help dramatically. Thank you very much for your contribution to the DATA world :)

[@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.

[@ommi3756]

Never get this clear until this video. Nice!

[@serhankars]

One of the best tutorials I've ever seen. Thank you so much. Brief and infomative. Animations are very helpful also.

[@VoluntaryDBA]

You're welcome!

[@akashverma1640]

This is all I was looking for. Best explanation about behind the scenes of indexing.

[@NatashaSalam]

Great video, thank you for creating this and explaining the concepts in a concise and visual manner.

[@Devilfairy1]

Best indexing explanation I've seen on internet.

[@tommccann3559]

Bravo! That is most succinct explanation of clustered indexes I have ever read or seen. I've got it now :-)

[@srapdy6960]

Excellent explanation. I don't think this can be described any better. Great visuals. Thank you so much

[@glebski1531]

really awesome explanation of a concept that I come across every day that has perplexed me to date... thank you sir !

[@akankshakaul744]

Excellent video. Finally I could find a video which is so crisp and clear. Thanks a ton!!

[@ckeveny1]

This is very useful. I now understand non-clustered indexes. Thank you

[@ArtemMikhaylov]

Perfect explanation I've ever seen before! Please do not stop!

[@TheJimboNJ]

Thank you!! I particularly liked your examples and your methodical delivery of the information. I found the examples to be very helpful as well!

[@tehawes0mesauce]

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! :)

[@js34lee]

you have saved my life !!!!! genius explanation. I have been struggling to understand this for months after months

[@manasr3969]

Excellent video. Much easier with visuals than reading articles. Keep up the good work.

[@ladhkay]

Most concise and easy to understand video out there. Thx man!

[@Akshay-Raut]

its simple to understand with graphical representation. Keep up with them. Great work.

[@AC-ft6mx]

Never it was explained so well by others. Thank you !!!

[@indric]

I understood more from this video than from a whole semester of lectures. Thanks!

[@VoluntaryDBA]

You're very welcome! I'm glad it helped you understand these concepts.

[@imrana.8370]

I had a hard time understanding the difference until I watched your video. Thanks for the simple explanation!

[@TijiMathewrjj]

Very well illustrated and explained thoroughly. Well done.

[@pradeepdesai9952]

Nicely put.. Specially graphical visual are the one which makes one understand much better .. .Thank you so much ...

[@condemned8916]

Sir 5/5 for this video , the visualization was a gr8 help in understanding . I had some knowledge that B-tree was the index data structure but could not grasp it , but after your video it helped me a lot. Plz do post more such videos.

[@roidelalune01]

Very consistent video. I hope you will add more on this topic. thank you very much

[@RucuryBeans]

Very useful, thanks for making the video and explaining the concepts so well!

[@ssaraswatipura]

Awesome presentation, looking forward to watching more of your presentation.

[@Yousafkhan-gv7cs]

Very helpful especially the way you explain and display the concept.

[@jaquesaulait]

Nice, clear delivery, good explanation. And he said "zed"! He speaks proper English..!

[@mehdizeynalov1062]

This man knows what he talks about - great. Waiting other videos.

[@mallaiahsomula1714]

Thank you so much, I never forget concept because of your visual representation. It made me to understand , very clearly

[@Jemmeh]

Great video, very well put together and simplifies the topic well.

[@georgesmith9178]

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.

[@ezequiel_code]

it can't be better explained, excelent work

[@hello-again6994]

great visual representation and model choice. subscribed!

[@pedropinto2192]

Very useful video! Your visual graphics made it very simple to understand. Thanks :)

[@nareshnama343]

Thank you ...very help full and wonderful demo..we are expecting to see more demos off SQL server from you..

[@kamalbalasubramanian621]

Best explanation with visuals. Kudos!!

[@gauravbabbar9808]

Best explanation i have seen for this topic. Thumbs up man.

[@programmingbeasts4649]

The best explanation of the indexes in SQL thank you so much

[@DownBeatTime]

The models you used were great! Thanks!

[@Major_Mason]

I am just starting to learn SQL. My dad is going to give me lessons, but this certainly helped me understand some of the terminology. I figured since I am already a Network Engineer who is two months away from his bachelor's degree, I want to make myself more valuable.

[@khaleda4873]

You are so chill bro, thanks for the video.

[@peeyar2000]

Great stuff about indexes.. Thanks for uploading.

[@sathwicksv]

Thank you very much, I have been reading at many places but no one explained with images. Greate video. Even MSDN documentation doesn't have this much information.

[@viveksingh100k]

Explained in very short time .. Thanks very much :)

[@user-ij2xw5qv6m]

Buena explicacion, estoy dando mis primeros pasos en SQL server, y tu explicación me aclaro muchas dudas

[@KanagaveluSugumar]

Wow, Excellent content and animation. Thank you!!

[@pablocazares4521]

very good! much better then others I've watched

[@mvmassoudi]

Very Professional, clear and informative; I also loved the video animations. Thank you

[@VoluntaryDBA]

You're welcome!

[@xiaoyi7538]

Thank you so much ! You are amazing. Everything is explained so organized

[@bobbysugianto5744]

what a brilliant explanation! subscribed!
Looking further for your explanation about physical and logical operators in SQL Server and when is the best situation to use it (Nested loops, Hash Match, Merge Join, etc)
Greetings from Indonesia!

[@iainelder7607]

Thanks, Jon. I liked the visual example of the phone book - helped me to understand how indexes work without getting bogged down in bytes and pointers.

[@VoluntaryDBA]

You're very welcome! That's exactly what I was going for.

[@mohsenhs]

Awesome tutorial, Visualised and explained well, Fantastic, Many thanks

[@reinersitanggang]

A lot wannabe blogs explained it with much much worse example, even a lot that even do not define from the scanning process through accumulate the results. Nice vid!

[@williamchin-fook8097]

Great Explanation and analogy about clustered-indexes 5 star!

[@pradeepn6328]

Nice Video, The way he explaining is extraordinary

[@brendaolson5912]

Very good explanation of the subject.. Thank you

[@caginbektas]

That was so helpful. Thank you for the clear explanation.

[@Watch-N-reWatch]

Thanks Voluntary.. This video was awesome.. I have been a years in Database but its first time I came to know what index is all about.. Thanks for your great example and way presentation.. U guys ROCK!

[@VoluntaryDBA]

You're welcome!

[@csmanul]

Thanks for explaining, i appreciate your effort.

[@dominicinzerillo7055]

Great stuff, made so much more sense then the books i have read.

[@VoluntaryDBA]

All it takes is one "ah-ha!" moment, no matter where it comes from. :) Thanks for watching!

[@marcchen4574]

I went through many other tutorials, this one really stands out

[@michaelkennedy5126]

Thanks friend, that was a clear and concise explanation with excellent graphics.

[@AlphaWatt]

Excellent explanation. This truly helped.

[@naveenkumar7262]

Thanks for this nice video. It was short, simple and easy to understand.
Thanks again!!

[@VoluntaryDBA]

You're very welcome! Thanks for watching.

[@MegaMajboor]

A great and understandable explanation! An outstanding video. Plz keep it up. Thanx sooooo much

[@VoluntaryDBA]

Thank you very much, and you're welcome!

[@angelogramatica9967]

Wow! Best explaining ever!

[@GhOnAu]

Great work, learned quite a lot about such a important topics in database the slides and visual explanation was piece of master piece

[@troop53no]

Thank you! I interact with a SQL database often, but indexes are not something I deal with enough. This was great information and exactly what I needed (:

[@nasarazam]

Precise and very well explained.

[@INvestYOU]

Excellent demonstration.

[@Njoiraja]

Nailed it. You earned a Subscription from a fellow DBA!

[@vivaladida3130]

very good job at explaining it, after so frustrated by my friend's explaination

[@CorbinBohne]

This is a fantastic explanation that a lowly analyst like me can understand :)

[@uskumart]

Great information! Looking forward to get more from you!!

[@VoluntaryDBA]

Thanks!

[@dineshsekar156]

Great Stuff. Nice Explanation. Thanks