Database Normalisation: Third Normal Form
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- เผยแพร่เมื่อ 9 ก.ค. 2024
- This video is part of a series about database normalisation. It explains how to transform a database, which is already in second normal form, into third normal form by working through an example. It covers the criteria for the second normal form including ensuring that a relation does not contain any transitive functional dependencies. The video reviews what is meant by a functional dependency and goes on to explain what is meant by a transitive dependency with examples.
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Thanks for using the same example in all three videos
That was the best.... Unlike others I saw
Seriously! Much easier to understand this way
Love these videos. Very helpful for explaining normalization. They're much easier to understand than most videos out there. It's also nice to see some humor thrown in.
I honestly admit after hours spent on searching for videos about database normalisation, that this is the clearest one that i found. Congrats and thanks again, you saved my day. I finally got a good understanding of the topic.
Quality examples, simple and clear explanations in all 3 videos about Normalization. Thank you, great work friend!!
Simple and straight forward, thank you!
This is an excellent deconstruction and has really cleared things up, thank you!
this nf series of videos is my go to when i need help with db schema. its explained so clearly
with this the second normal form became also clearer, most understandable videos that i found, thank you
Excellent explanation without unnecessary jargon. Thank you.
Great video series, thank you very much!
Thank you for explaining this in such a consistent approach. Great set of videos.
You're very welcome :)KD
This is an amazingly simple explanation. Thank you
You are the GOD(Greatest of DBMS). No other youtube video could explain Normalization in a way that you did. Really feeling confident now. Thanks a ton! :-)
You are very kind. :)KD
@@ComputerScienceLessons Thankyou :-) Could you Please post a Boyce Codd Normalization explanation too? I understood the 1NF, 2NF, 3NF, thanks to your video. But I am unable to understand BCNF(mainly the "multi-valued dependency" concept) Thanks for your help bro :D
Really thank you. Your videos are always so amazing.
best explanation of normalization on the internet! thank you
Thank you for saying so. :) KD
Thanks a lot. It really helps me in understand those three normal form.
Please make also for BCNF... I really had a hard time understanding this concept BCNF Thank you.
You did a great job!
Thanks for your work. I agree about how effective it was to use the same examples in the 3 videos.
That helped to normalize the videos with the normal form number being the key 😅
You are most welcome :)KD
Greatly explained, thank you!
i have a question, you said the grade is drived from exam mark, and it is violated 3NF, and we need to create a new table: result. but what primary ID should we set for result? right now, i am doing my project, i have a table: BillingInfo (billingID, bookID, number_of_book, price), the price is drived from bookID and number of book, so i guess i need to seperate this into two tables, but i don't have any idea how to decomposite a new table
thank you for explaining in detail with examples and in simple words.
Youre welcome
God bless you immensely for this... You're really a good teacher
Really appreciate the comment. Thanks :) KD
Thank you so very much. I was searching for one examplé tha fits 1,2,3 normal forms and luckily I found yours. Thanks much again
Best Normaization video in the universe for night before exam.
U da man. Thanks for the informative video 💪🏽
Thank you. You are most welcome :)KD
Best video on the topic, period. I wonder why other videos have more views than this one.
Thanks for the lovely comment. I should probably put more effort into publicising my channel - but it is growing organically. Please spread the word. :)KD
@@ComputerScienceLessons Hear, hear. Thank you for this!
Best Explanation
I can't find a video from your channel about BCNF. Are you able to create one, please?
Thank you for the easy to understand videos
You're welcome. :) KD
Crystal clear!
Thank you :)KD
Thanks a lot 👏👏👏
great video! thanks.
You're welcome, and thank you :)KD
I have a question (excuse me if this is too dumb😅): Isn't the Last Name also dependent on First Name? For instance, if someone else has to be assigned the same id as Kevin Drumm, wouldn't we need to change both the last name and the first name? Shouldn't this also be a violation of 3rd normal form?
Life saver thank you!
You are most welcome :)KD
Best Explanation. thanx bro❤
You're welcome :)KD
Thank you
Thank you.
You're welcome :)KD
OK thank you Bro makes sense
Hi! I like your videos because its easy to understand. Im struggle to make a slides for my presentations and I'm also new in IT field huehue, but do you have a videos about the advantages of relational database?
Soon we will be forced to put genders in a separate table as well, since people are starting to change them regularly as they change address :D. Thank you very much from Rome, it was a very beautiful tutorial!
You are probably correct. Thanks for the lovely comment. :)KD
Awesome video
Thank you :)KD
Thanks very much.
You're welcome :)KD
You have the best voice.
You are very welcome non breaking space :)KD
Maximizing information content (sentences) from given amount of data (words) derived by relational logic.
Appreciated :)KD
I want to take these courses with these professors.
Wouldn't the last name dependent on the marital status, if its a female, therefore not be in 3rd normal form?
Debatably! I'm sure there are plenty of females who did not change their last name when they got married who would argue against that. :)KD
Great
work
Thank you :)KD
Thanks sir
there is already a partial dependancy as well. where course tittle, teacher id -> teacher name and teacher id -> teacher name. so it cannot pass through 2NF..correct me if i am wrong
I'm confused. In your 2NF video, you say "a table should only contain data about one type of thing" to be in 2NF. But in Courses (at 3:30) it clearly contains data about two different things - Courses and Teachers. So I don't understand how it is in 2NF? I'm lost on the difference between 2NF and 3NF.
Hi Dominic. In this specific example, each course has its very own teacher and there are no teachers here that teach more than one course, so, arguably, the information about each teacher is actually information about the course. If however, Mr Einstein taught Chemistry AND Physics, then the Courses table would not be in 2NF. You could also argue that since some of the courses have the same Fee, then the Fees should be in a different table to meet the criteria for 2NF. In the past I have seen problems in which the data were totally abstract (letters and numbers only, and column names like Col1, Col2, Col3, etc.). Theoretically, you can normalise such tables by following a set of rules. I must say however (at the risk of muddying the water for you), I see little real world value in abstract problems like this. It's more important to know your data and what you want to do with it; common sense and and instinct play an important role in database design (someone will probably object to that statement!). You are therefore correct to say that a teacher is a different thing and belongs in its own table. A final point, a fully normalised database is not always the best solution to a problem; take a look at NoSQL. :)KD
love it
Thank you :)KD
so many ahh ha moments wish i found this before all the other videos that ive been scraping through.
He is an example of a Great Teacher. They are hard to come by. There are other videos on this very same topic that are not explained as well as this person does it.
7:32 "Every student has a gender, but it doesn't really make sense to put genders in a separate table."
Had a nice little chuckle out of that one... with the way multi-gender culture is going...
Do attributes that are foreign keys have to follow the same rules?
Attributes that are foreign keys are not particularly special. Any attribute can be a foreign key.
@@ComputerScienceLessons So a foreign key can be normalised out of a table?
Why do we not need a course ID in this case?
Because, in this scenario, the course title is unique and can therefore serve as a primary key. In practice, a course ID might be included because it can save confusion when you have similar course titles, and it's easier to quote when people make bookings.
I wonder why the courses table doesn't have any ID.
Hi Nadeesha. As long as a table includes a column with unique values, then this column can serve as the primary key. If the Course Title is always unique, this can be the primary key. If a COMBINATION of columns for any given record is always unique, then this combination can serve as a 'composite' primary key. What you choose for a primary key depends on the nature of the data. Having said that, I've worked with a number of organisations where database designers were encouraged to always include a surrogate primary key (a single column whose only purpose is to serve as a primary key). In this example, you would include a new CourseID column. This makes life easier for people programming the front end. :)KD
@@ComputerScienceLessons If the course title could change (e.g. from Mathematics to Maths) would that make it inelligable (or maybe just a poor choice of) primary key?
Felt like watching a david Attenborough documentary.😍
Thanks for the complement :)KD
the best
TY :)KD
Great examples! But unless you previously defined key and primary key in some nonstandard way, I believe your definition is slightly inaccurate.
AFAIU wherever you said "primary key" you should replace it by "any candidate key", and then by a "non key" attribute you presumably mean a non-prime attribute, that is an attribute that is not part of any candidate key... because every attribute is at least part of the whole scheme as a superkey.
I see where you're coming from. However, I often find that colloquial language better aids understanding. Nuance comes later. :)KD
would you please make a video on BCNF
I will try to do something soon. Busy at work at the moment. :)KD
Wouldn't the Last Name have a transient dependency on the marital status? When someone marries they might take another last name ;)
I think that depends on your politically correctness ;)KD
Would fees not have its own table since there are duplicate fees, e.g. 1800 for Physics and 1800 for Chemistry. So a table called Fees, which has Fee ID (primary key) and fee (int) and hell... even Qualifcations could have its own table too. Actually, I think that might be 4NF...
I saw a sherlock reference there
Elementary my dear Bi el
Can i use noodles for making database?
You can do whatever you want! :)KD
That last example fails if the exam is graded on a curve. In that case, the letter grade is free to change independently of the exam mark.
Fair point. Horses for courses.
7:42 all 'The Simpsons' fans will see it
Doh!
2:26 "transient" should actually be "transitive" (I believe!)
You are quite correct - oops! (I will upload a fix)
@@ComputerScienceLessons thanks for the excellent video! I found it super helpful :)
:D
:)KD
Bro where do you go to school where a 70 is still a B?
I mark hard. :)KD
Can you help me teacher???
imagine being married while doing A levels lol
It depends who you imagine you are married to... :)KD
Database is such a fcking boring ****, but loved the video
In todays world I think it's inevitable to separate gender table on its own.
You are wrong, the data must be in least the first normal form, it doesn't have to be in the second.
It depends on what you are trying to achieve. Indeed, you may not want your data normalised at all. :)KD
Poor example, it should not take 8 mins to state the 3NF and give a clear example smh
nyl
Thank you sir
You're welcome :)KD