Learn Database Normalization - 1NF, 2NF, 3NF, 4NF, 5NF 

CORRECTIONS: Expand this comment to see corrections. CONTENTS 0:00 What is database normalization? 3:55 First Normal Form (1NF) 10:24 Second Normal Form (2NF) 16:08 Third Normal Form (3NF) 20:29 Fourth Normal Form (4NF) 23:47 Fifth Normal Form (5NF) 26:41 Summary and review *** CORRECTIONS *** In the Fourth Normal Form (4NF) section, at 23:27 the primary key for the Model_Colors_Available table should appear as {Model, Color}; the primary key for the Model_Styles_Available table should appear as {Model, Style}. Also, the video's informal definition of 4NF - which states that multivalued dependencies on a non-key aren't allowed - is a little too simplistic. I should have said that what's forbidden are "non-trivial" multivalued dependencies on a non-key. "Trivial" multivalued dependencies on a non-key - like Model ->> Color in the case of the Model_Colors_Available table - are fine! A multivalued dependency is considered trivial if the attribute(s) on the left side of the arrow (in this case, Model) and the attribute(s) on the right side of the arrow (in this case, Color) together make up all the attributes in the table. In the First Normal Form (1NF) section, at 4:42, since the column heading in the query results is Beatle, the query itself should have been shown as selecting Beatle. (The query is erroneously shown as selecting "Member_Name".) In the Fifth Normal Form (5NF) section, the summary at 26:16 says that a table (call it T) violates 5NF if it can be "logically thought of as being the result of joining some other tables together." I should have clarified that it if those "other tables" all have the same key as the table T, then it doesn't count as a violation! For example, the fact that a table with columns ( Product_ID (PK), Product_Name ) joins to a table with columns ( Product_ID (PK), Product_Color ) to yield a table PRODUCT which has columns ( Product_ID (PK), Product_Name, Product_Color ) doesn't mean that PRODUCT violates 5NF. More generally, I now think there was a little too much looseness in my presentation of 5NF; I'll do a standalone 5NF video at some point that describes 5NF in a less question-begging way. The same goes for 4NF!

Sometimes I hear explanations such as this and wonder how other people have such a difficult time expressing the same idea. Yours is so concise and well broken down, avoiding convoluted terms and making good use of analogies. Thank you Decomplexify.

this is the clearest explanation about database normalization so far. You have my gratitude

I’ve been building databases for over 20 years and this is one of the simplest and clearest explanations I’ve ever seen.

A lot of these normalisation forms once you've learnt them just seem so natural that it's hard to imagine not doing them.

I've used SQL databases for longer than a quarter century. Even longer ago, I studied this as part of my CS education. I saw this video in my stream just now, and thought I'd refresh myself. I was very pleased as it confirmed what I've been doing in my professional career. I guess something stuck deep inside my neurons so many years ago! Excellent video, very well explained with very good examples! Great work!

Stuff I’ve known for years, but never explained so concisely - kudos to you great work 👌

You summarized 2 whole days worth of lectures into 20 mins, thank you!!!

Thank you! You obviously have a knack for explaining things. The animation is really nice and helps with the subject. Can't wait for more.

What a gem you are!! 5 normalization rules in under 30 minutes, so clearly. Just WoW! Thanks a lot for making me understand all of it. You deserve 2.24million subscribers not 22.4K.

its honestly criminal that you dont have more subs. i wish I could find a video this well done on every topic I struggle with

This was immensely useful as the rigorous, mathematical explanation given to me in university wasn't clear enough. Thank you! You've got a new subscriber, and I hope I get to enjoy your future content :)

Nice work Decomplexify! Easy and clear, one of the best explanations that I have ever watched.

By far the best explanation on Normalization I have been able to find! Keep up the great work!!

That's without a doubt the clearest explanation I ever heard about database normalisation forms. Your videos are incredibly good. TY

Wow. Of all the videos about database relationships in youtube. Yours is the only one that is complete in details. Thank you.

One of the more clear normalization explanations here! Good job!

There does not exist a better video that explains normalization with such clarity and simplicity.

I had to read a chapter on normalizations for my database class and I was just lost with the usage of its jargons. This video helped it alot! Simple and thorough.

This has been hugely helpful! I was completely lost with Normalization but not anymore. Thank you

The best explanation available. Normalization is so easy after watching this video, and it all makes sense. Thank you so much!

Working with DBs 25 years (since SQL6.5). This is one of the most complete and clear explanation I have seen

Someone give this guy a teacher's award - One of the best breakdowns of a difficult subject I have seen

You're a wonderful instructor, and there are many leaners in the the world who need you..Thank-you

I don't know how many books and articles I've read that don't explain this, but you did. Keep up the good work!

Though not part of the normal forms, I would also add don't use something that might change as a primary key, such as player name if players are allowed to change their names. Then you have to update all the tables keyed by that player. Better to invent a player ID number, use that as key and store the (name,id) pairs in a table.

So clear explanation. Well done. I read this long time in university, but I have long since forgot the definitions. Thankfully I have always ended up fully normalized 3NF designs since it makes intuitive sense. Having met non-normalized designs at work, the pain those caused were enormous and stalled the development (eventually bankrupting the company)… FUBAR, it was.

Definitely the best explanation ive seen for these normal forms!!! I learned this in school and after a while I forget the rules, I just know whats needed in a table. I'm glad to take this refresher and take note of them. I find after designing many tables, these rules tend to happen organically because if not you run into too many problems.

This has been by far the most clear, concise & practical explanation. Thanks!

Subscribed! I'm currently studying this subject because I've an exam in 2 days but, I've decided that I will continue watching your videos. The way you explain things is out of the ordinary. Thank you!

This is EXCELLENT! So easy understand without unnecessary mathematical rigor for us mortals ;-). Thank you Mr. Decomplexify for those awesome explanations.

perfect pacing, no bloat. Highly appreciated; intro's and padding are the bane of self learners through youtube

Concise, well illustrated, yet densely well organized video structure. 10/10 Thank you will repost!

You're great, keep up doing the amazing stuff. You'll be getting what you deserve ultimately.

I really wish I were as eloquent as the creator of this brilliant video. Literally none of my questions pertaining to the subject are left unanswered. Thank you!

Seriously, I can't thank you enough for this, the database course in my university made this look like a convoluted mess and you just explain it so simply like that

Excellent presentation of normalized forms. Given so much noSQL databases these days, it's nice to be reminded of data safety concerns...

This is a great video! I think that a video on different keys and what they are would be really helpful as well!

This is a gem. Please make uploads more consistently. Thank you.

I was having a really hard time with this concept and this video made it all click. Thank you so much. Looking forward to your content going forward

This is awesome. Much appreciated 🙏 Edit: would love to see a similar decomplexify centred on the models used in reports created via data analytics? How to approach creating the optimum data set in terms of structure, such as a star model versus other options whose names I haven't yet looked up 😊

Seriously the best video explanation. Other youtube videos only cover a few cases. Or don't explain each normalization clearly. Great videos. I subscribed. I am a front-end dev expanding my skillset to more full stack. Databases are my weakest area. Really appreciate the in depth well thought out content!

Thanks for this! Like others, I'm studying for a databases exam and needed a fresh explanation of normalisation. This video helped me refine my notes and cement it more in my brain.

Where was this explanation when i needed it in school! This is a really awesome description and it is timeless

Seriously the best explanation ever ! Thanks a lot Sir. 😍

I've done the LinkedIn Learning videos my university provided, nothing. I've powered through the reading materials left and right, still nothing. I've tried other RU-vid videos, and surprise, still nothing. Your video somehow makes it make sense. I've been struggling with these concepts for 2 weeks now. Thank you for putting it in basic terms!

A very long time ago (1996ish) the two guys who did all of the non-AS400 report writing both quit at our company. They were friends of mine, and both told their managers that I at least knew how to code in BASIC, and as all the operations reporting was in VB (mostly excel, some Access), I replaced both. I used their old Excel-based reporting system for awhile, but HEAVILY gravitated to Access (we weren't IT, so "When all you have is a hammer..."). Seeing all this laid out like this is kind of refreshing to see. Normalization -- self-taught as I was -- eventually got so ingrained me that I randomly build databases to organize things at home. Thanks for this. It's good stuff.

"I hope you find this video helpful" - I find this video way too helpful. Thank you so much for making things so clear to understand. great job.

Well done mate! Your explanations were absolutely brilliant!! Keep up the good work and Thank you !!

This video actually is really very helpful. I dk why you have so less views. You deserve more.

Absolutely loved this video. Learned a lot about normalization, but also communication and teaching. Thank you.

in my first proper job, the content of these 30 minutes was basically all i needed to know to be a "specialist in database design" :D

I remember learning this on a Systems Analysis course in 1985. Inefficient databases could have a real impact on performance whereas today poor database design can be masked by more powerful hardware.

Bro.. thanks! You made it so simple.

This is a phenomenal explanation. So simple and direct.

This video is so great. I am a relatively new business analyst and have been struggling with a non-normalized legacy database that has been causing a lot of headache at my job. Can't wait to get in there and get it fixed up after watching this! Thank you Decomplexify

Firstly, this is a delightful and clear explanation - thank you! It makes me nostalgic for the time when I would regularly hear such formalisms discussed in corporate IT settings. One of the difficulties you must encounter when teaching these concepts in the current era is that contemporary thinking in software engineering encourages designers to think of databases as _merely_ "storage" or "persistence" for an individual application. An implementation detail, trivial in to the real work of the system. Whereas Ted Codd and Chris Date conceived of the database as the information system itself. It would enforce universal logic and consistency. It was the main event. Applications that made use of the data would come and go. And they would adapt themselves to its schema, and its declared and transparent logic. (Transparent in its original sense, not in the way it has come to means its opposite - a black box.) Codd didn't predict a world in which each application had its own database, and there was money to be made as an "enterprise data integration and migration consultant". My career thus far has brought me to the disheartening conclusion that a really useful information system in an organization of any size or scale takes so much time, effort, and co-ordination to build (and evolve) that before it has reached even a third of its potential, there are already multiple generational conflicts around its intent and purpose.

In a few years' time this video is bound to have milions of views. Congratulations on such an amazing (and simple) explanation!

I'm very glad to see someone able to articulate this somewhat esoteric topic so eloquently and succinctly! My initial foray into DB started at home on a PC with a copy of IBM's DB2 for DOS that a dad of one of my mates... ahem... acquired for me. This lead to an entire lifetime of love for and a career in databases and data integrity, starting with teaching database theory and design at my university as a postgrad to finally running my own IT school where I teach database theory to the advanced highschoolers. Educative content such as this is so valuable to those coming after us... Keep up the top notch work!

Really awesome video. I'm taking a class on relational database design and the lecture I attended on this topic was very convoluted. Your presentation and examples cleared everything up for me, thank you.

Normalization your gateway to “left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on left join on”

The best explanation of DB normalization that I was able to find on RU-vid. Thanks a lot man!

Best Video on the internet to explain Normal Forms in easiest way.. landed here after skipping many confusing videos. thank you !

Great video! I would say the issue of repeating groups in 1NF isn't clear about the repeating group. A repeating group is more than a multivalued attribute. It is a repeating group because, in your example, the quantity and the item belong together. In the first row, player jdog21 isn't just associated with multiple quantities and multiple items. The quantity and the item are associated (e.g., 2 with amulet and 4 with ring are correct, while 4 with amulet and 2 with ring would be incorrect). A multivalued attribute should be separated into a different table, as you showed. But, if the quantity and item were not related, then a three table design would be better {(player), (player, item), (player, quantity)} so the 4NF problem isn't created. What makes it a repeating group is that the association of the first value of quantity with the first value of item, the second value of quantity with the second value of item must be maintained.

I’ve been a database engineer for 25 years and this stuff is still super useful. Thank you

What memories. It’s nearly 30 years since I looked at normalisation. This video bought back many memories.

The importance of this video cannot be overstated. Well done.

using this videos for university... and it's clear htat you know the subject to perfection, otherwise you wouldnt be able to explain it so brightly clearly. Thank you very very much man.

Best video I have seen on this topic. But just a little concern is that at 23:27 why model column can have duplicate values? Isn't it primary key?

Good explanations! One criticism: I was confused what First Normal Form (INF) meant until I realised that the letter I was a digit 1. It might be better to use a font that makes these two characters more easily distinguished.

The most concise explanation of Database Normalization Form ever read!

Perfect, I learned all this stuff in high school over 20 years ago. After watching this everything was clear again

I'm so happy I found your videos about normalization. I've been struggling to understand the topics really and I have an exam in database in a couple of days and after I saw your video it made so sense. Thank you for making this videoes :D

Hey thank you for this. I'm in a master's program and this was a super simple and understandable take on this

Really clean and easy to grasp content. Great work!

Thank you so much sir. I learned more here than I have the last 5 weeks I took in my database class

The best tutorial for a topic I have ever watched on youtube.

I've worked with Relational Databases since 1983 (when IBM released DB2) and this is one of the best and clearest explanations of normalization I've ever seen.

This is a very clear explanation, you’ve earned a sub. Can’t believe you don’t have more subscribers.

Wonderful explanation and tutorial, thank you! ☺️ I am sure that many students are as grateful as I am for this video 😊

I have spent half afternoon studying the DB normal forms, and wish I had found this video before all the others I have watched. This was in fact the only worth watching, so far.

This is excellent! Explains it absolutely well. Keep up the good work!

Well that was two weeks of lectures summed up nicely. THANK YOU!

This is how it works! 👍Great explanation! Even if the most work is involved, the 5th normal form is the easiest and “cleanest” to work with.

Elegant and simple! I love the way you do it. Keep it up!

this is an amazing video, I had to see it like 4 times because I'm learning but it's really well explained, thanks a lot!

Great video! Easy to follow and good explanations. Thanks!

Thank you so much for this. It's amazing how much easier you taught me this than my university did

This is phenomenally well explained and invaluable - this has made my life SO much easier! Thank you!

Wow.... This is the best database explanation I've ever seen. Thanks a lot!

Been a long time since I last revisited the 5 NFs, impressive video, really like the slides and not being a typical powerpoint thing. :)

Your "real world examples" seriously helped prove your point, because my uni reference material has similar-ish theory as you, but the examples are absolutely bad in them... your video seriously clears up a lot!

Best Normalization explanation I have ever seen. Thanks!

Love your channel! New sub here! keep it going! Love all your videos! Simple and straight to the point.

Thanks for this. You have given me a way to fix many problems at work. Inspiring!

Damn. This is an impressively approachable and brief explanation.

Thank you for this. I leant relational database practically (using tools like Airtable etc) but never leant it theoretically. This is is so easy explanation who wants to know the basics.

This video helped me solve the constant urge to slap a json list in a database whemever i have a list of things (inventory example) Thanks!!

Best Video on normalization. Thank you for making this absolute gem of a video !

This is awesome content, man! Made things much clearer now.. so, thanks so much! I'll sure check out other videos as well. Keep up the good work.