If you made it this far, you actually want to understand this stuff properly 👍

I turned everything I know about normalization into a full e-book — with in-depth / expanded discussions of all the normal forms including BCNF / 4NF / 5NF, exercises and solutions, and a lot of detail I couldn't fit into this video. Plus a 🎁 BONUS interactive SQL facility to help you explore tables with normalization issues. 👉 https://decomplexify.org/p-dbnorm if you want to go further.

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

Want a free PDF quick reference guide covering 1st, 2nd, and 3rd Normal Form? Get it here: https://decomplexify.myflodesk.com/wm7ixaj2x6

* 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!

imagine yapping for 8 hours about this just to be outplayed by a random guy on youtube in 28 minutes

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

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

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

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.

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.

Your most replayed wave in 3NF part of the video looks like Saddam Hussein's hiding spot😭😭😭 Great video btw

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

This was popular for a while and then everyone forgot it.

I've been building databases for over a century and this is the best video I have ever seen in my life

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

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.

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

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

Now I understand Normal form❤ Good attempt ❤

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

You taught me what my clg was supposed to.........
Thank you for that 🙏

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.