Thank u so much.....mujhe abhi tk candidate key derive karna nhi aata tha bt apka ek single video dekh ke he mujhe candidate key ache se aa gya....rocking tutorial nd ur teaching technique is too good...pls give some more examples of canonical prob...
Lifesaver. I am currently a student from UNSW and the course: database management was given by a Chinese PHD student who only knows how to read the PDF instructure without his own idea and explaination. Thanks again for helping me to crash the assignment.
@@muhieddineshebaro6635 Wow.. I posted this comment 5 years ago. Yes I got my degree 5 years ago and and now working as a senior software solution architect for a major tech company :)
@@mrk_2019 omg lol. I did not expect you to reply. Congrats on your degree. Hard work which shows by your comments pays off xD screenshot them and keep them as memories
I think qus ask for finding the c.key, so by definition c.key is minimal super keys. so after taking 2 combination we have to stop, no need to proceed further.
no other lectures give this simple explanation. In the Beginning i thought it was not effective because it is a old lecture don't think like that it is the best lecture on candidate keys😍
You are the best bro, No book explain this much better than u do., Ur videos series are very nice , i became fan of yours , super job, keep helping others
My DBMS lecturer only explained about the normalisation and functional dependencies,but did not explained the main thing i.e. hoe to find the candidate key which you explained very well. Thank you
Why D+ (closure) is not considered as a candidate key? In previous video you said that the attribute which is not present on the right side can be included in candidate key
@@falguni1185 but there is in ACE test series it happens, all the attributes were at right side that's why i marked 0 key as answer but they had given 4 candidate key in their original answer now I'm stressed why these all happens without some logic Btt now i got everything from some source that if everything is present on right side doesn't means there is 0 key there might be some keys btt not necessarily to have any attributes in every candidate key
For this question: R = (A,B,C,D,E) A -> BC CD -> E B -> D E -> A All the attributes are present of the right side,ie, A,B,C,D,E. So do I conclude that there is no candidate key in R?
Good Video.. But I give you an Example where you the principle seems not to work: (A,B,C) ; A -> B, B->C, C->B ..so in this scenario every attribute is a candidate key..
i have a question which is that,,when i got that ' D' is not present in the right we started making pairs wd D to find the candidate key right.but my qustion is to find candidate key is it mandatory that always we have to make pair up with D to find candidate key?
yes since D is not present on the Right side, it is necessary that it will always be a part of Candidate key. Lets say there's an attribute X in a relation/table, and its such that no other attribute determines X(only X determines X itself), but in the table we need a Key that will always determine the records uniquely, in order to X to be determined no other attribute will be sufficient hence to determine records X will always be there in the Candidate/Primary key.
What if on right hand side you got all the elements.. how do you find the candidate key R={ABCDE} A->BC, CD->E, B->D, E->A . FIND ALL POSSIBLE CANDIDATE KEY
Sir, i have a question that, as we know that ,the attributes which are not present in the right and side are present in candidate key. BUT ,there are some questions where all the given attributes are present on the right and side . SO, on that case what condition / or which attribute we have to consider for candidate key ???
Nicely Done....just 1 thing... Can you re-explain your last word i.e. when I got ,say 4 Ck's, and I am doubtful that there may be one more CK so the answer might be 5 and not 4, then in such situation how should I confirm myself that there can not be any further CK's in this Relation?
I have a question, if i have sets of 2 attributes that are in the set of candidate keys, is it useless to check sets of 3 attributes? Because the definition of candidate key is: A minimal set of attributes necessary to identify a tuple
There is a way to know when you don't have to go on to higher element amounts and check, but I forget what that is. Seems like it would be very important in a problem like this though...
I just looked it up. It's because one of the conditions to be a candidate key is that NONE of the subsets in a candidate key are allowed to be a candidate key. Since we have DA, DB, DE, and DF as candidate keys, this would greatly reduce the amount of other combinations available to you and the rest didn't work out according to the presenter anyway. I hope that helps anyone who cares to know. Haha
sir how many combinations we must have to take if we are not giving any mcq type exams rather in which we need to solve the full problem, and as u have found candidate key can u tell how we can find super key.
Hello Sir, I'm still in doubt. You told that we need to check more combination if possible in this question but Candidate Key is nothing but minimal Super Key then if there are other possible then why should I try them? For Example : In your example why should I move to using 3 values (DCH Closure) ? Give any Counter Example to clear my doubt! And Your teaching way is really awsome ! Thanks a lot and keep making more videos.
I don't think [CHAD]+ is a candidate key as [DA]+ already is a candidate key, so there is no point of having a combination of another attribute with a candidate key.
+Supratik Majumdar [AD] is already a set of candidate keys, so [CHAD] must be a set of candidate keys, the only problem here is you only need to find the minimum candidate keys.
A candidate key is the minimal super-key for a relation. Notice that DE is already a canidate key. Then any other key that has DE in it, like DEG or DEA or DEABC etc, is not a canidate key because, while it is a super-key for the relation, it is not the minimal super key
how it can be 4 candidate keys only where we can also have dab dac dae daf dag and many other as candidate key!! logically dac dae dab etc are also subset of the relation attributes!! isnt it?
9 years later, it is still helpful. thanks man
Sir*😂
Man * not Ma'am 😂@@Dreamerrrr__007
You're the goat bro
- All CS students worldwide
not just this video, your all videos which i watched are probably the most clear and not time consuming videos about this topic
our DBMS lecturer recommended your channel in class, thats how awesome your explaination is. thank you so much ! :D
please join on techtud.com
Your doubts will get answered there really quick.
Thank u so much.....mujhe abhi tk candidate key derive karna nhi aata tha bt apka ek single video dekh ke he mujhe candidate key ache se aa gya....rocking tutorial nd ur teaching technique is too good...pls give some more examples of canonical prob...
Thank you for your great work!!!!
5 years later still very helpful. Thank you for posting this, it makes so much more sense the way you explained it!
8 years
Even after 9 years, no one can beat this legend
9 year's still helpful
Mate, you have gifted my 10% in one of my master's papers. Really appreciate the tutorials.
Lifesaver. I am currently a student from UNSW and the course: database management was given by a Chinese PHD student who only knows how to read the PDF instructure without his own idea and explaination. Thanks again for helping me to crash the assignment.
are you from alliance university or wot bro💀
You saved my life bro....... Just understood this few hours before my final exam..
Did you succeed your exam? Did you get your degree yet or what?
@@muhieddineshebaro6635 Wow.. I posted this comment 5 years ago. Yes I got my degree 5 years ago and and now working as a senior software solution architect for a major tech company :)
@@mrk_2019 omg lol. I did not expect you to reply. Congrats on your degree. Hard work which shows by your comments pays off xD screenshot them and keep them as memories
sup@@muhieddineshebaro6635
9 year's still helpful
One of the best tutorials about how to find candidate key
Thanks a lot
I think qus ask for finding the c.key, so by definition c.key is minimal super keys. so after taking 2 combination we have to stop, no need to proceed further.
dude you are awesome
no other lectures give this simple explanation. In the Beginning i thought it was not effective because it is a old lecture don't think like that it is the best lecture on candidate keys😍
Man you are a lifesaver as well as a timesaver!
You are the best bro, No book explain this much better than u do., Ur videos series are very nice , i became fan of yours , super job, keep helping others
Nice :") I finally find the explaination that will allowed me to continue to read my lecture slides
Your style of teaching was so understandable..
8 year later ,it is still very helpful
you teach even better than the university professor
Nice explanation now my concept got cleared after 1.5 month thanks once again
One of the best explanation so far
My DBMS lecturer only explained about the normalisation and functional dependencies,but did not explained the main thing i.e. hoe to find the candidate key which you explained very well. Thank you
Beautiful easy explanation . Very simple illlustration .
The best channel for DBMS. Good work!!
woh its been 10 years and this video is so accurate ...
a best way to study and preparation for GATE
Did you have to check all possible subsets of the relation? How could you rule out certain paths without checking everything?
Why D+ (closure) is not considered as a candidate key? In previous video you said that the attribute which is not present on the right side can be included in candidate key
From d you can't visit other entities that's why d is not candidate key
really nice..Makes my concept is very clear..thank you..
Thanks my man! This was so helpful!! Really good explanation
Very Helpful, keep up the good work.
how do you choose a key from the candidates now? Can you just randomly decide which one you want to take?
omg! Thanks so much! you are my lifesaver for final tmr
Better explanation then our professors
You're the greatest man
what if all values are present in right side
Not possible. In such case every attribute is determined by some other which means there is no key.
@@falguni1185 but there is in ACE test series it happens, all the attributes were at right side that's why i marked 0 key as answer but they had given 4 candidate key in their original answer now I'm stressed why these all happens without some logic
Btt now i got everything from some source that if everything is present on right side doesn't means there is 0 key there might be some keys btt not necessarily to have any attributes in every candidate key
a very nice set of explaination to the database concepts...one doubt, [DABEFCH] won't act as a candidate key??
So, to find a Candidate Key it need all the letters to be on the right hand side? And we have to try any possibility to find as much as we can?
For this question:
R = (A,B,C,D,E)
A -> BC
CD -> E
B -> D
E -> A
All the attributes are present of the right side,ie, A,B,C,D,E. So do I conclude that there is no candidate key in R?
+Ilyas Habeeb There are a few candidate keys. Here are a few of them:
A --> ABCDE
E --> EABCD
AB --> ABECD
+Daniel Fratamico I think Ab wont be candidate key as A is already candidate key...
not AB, because it is reducible to A
nice q....thanks
@@danfratamico How can A determine D ?
very nice video having a small trick to find candidate keys quickly.
Amazing videos man.. Keep up the good work
Simple Nd understood.....very nice
Very helpful videos. Thanks a lot sir!
Thanks a lot. That was very useful and simple to understand.
Never knew this was so easy.
Fully Understood Thank you so much bro , you are awesome
Very Helpful Thanks for uploading
But sir.. How we will be so sure..,, there will be not another candidate key.. Like you say " I have tried " But how could we be sure with this??
Good Video..
But I give you an Example where you the principle seems not to work:
(A,B,C) ; A -> B, B->C, C->B
..so in this scenario every attribute is a candidate key..
thank you sir,your lectures are really helpfull
i have a question which is that,,when i got that ' D' is not present in the right we started making pairs wd D to find the candidate key right.but my qustion is to find candidate key is it mandatory that always we have to make pair up with D to find candidate key?
Yess.. A candidate key will not be present on the right hand side of the relation
yes since D is not present on the Right side, it is necessary that it will always be a part of Candidate key.
Lets say there's an attribute X in a relation/table, and its such that no other attribute determines X(only X determines X itself), but in the table we need a Key that will always determine the records uniquely, in order to X to be determined no other attribute will be sufficient hence to determine records X will always be there in the Candidate/Primary key.
I have a question, Since DA and DB both are candidate keys, why can't we consider DBA as a candidate key?
Thank you for your very helpful videos
VERY GOOD.........MAKES CONCEPT VERY CLEAR..........GREAT WORK....THANX ALOT
what if all of R was on the right hand side? will the candidate keys be combinations of the determining attributes?
thanks!
What if on right hand side you got all the elements.. how do you find the candidate key
R={ABCDE} A->BC, CD->E, B->D, E->A . FIND ALL POSSIBLE CANDIDATE KEY
Yay, I from CityU also recommend this one
Sir, i have a question that, as we know that ,the attributes which are not present in the right and side are present in candidate key. BUT ,there are some questions where all the given attributes are present on the right and side . SO, on that case what condition / or which attribute we have to consider for candidate key ???
Where is the question.
Still helpful after 10 years
Thanks m8! SO to India
Bro you are great 👍 👌
If every attribute inright hand side .. then which should take first
Nicely Done....just 1 thing... Can you re-explain your last word i.e. when I got ,say 4 Ck's, and I am doubtful that there may be one more CK so the answer might be 5 and not 4, then in such situation how should I confirm myself that there can not be any further CK's in this Relation?
I have a question, if i have sets of 2 attributes that are in the set of candidate keys, is it useless to check sets of 3 attributes? Because the definition of candidate key is: A minimal set of attributes necessary to identify a tuple
very good explanation.
thank you!!! It is really helpful
All the combination using DA can also be candidate key like DAB?
if sir all attributes present in rhs then how will define
thank you so much it help me lot !!
Should not (DBC) be a Candidate Key?
Candidate Key is minimal set of super key. DB is already a Candidate Key, hence you are not allowed to pair it up with any others.
@@rohitmondal6876 You are 2 years late mate. Then again, I am too.
can we make the combinations of D with attributes on right hand side, as they are the only remaining attributes to check for candidate keys?
There is a way to know when you don't have to go on to higher element amounts and check, but I forget what that is. Seems like it would be very important in a problem like this though...
I just looked it up. It's because one of the conditions to be a candidate key is that NONE of the subsets in a candidate key are allowed to be a candidate key. Since we have DA, DB, DE, and DF as candidate keys, this would greatly reduce the amount of other combinations available to you and the rest didn't work out according to the presenter anyway. I hope that helps anyone who cares to know. Haha
sir how many combinations we must have to take if we are not giving any mcq type exams rather in which we need to solve the full problem, and as u have found candidate key can u tell how we can find super key.
Hello my dear! can you please solve some good exercises of normalization?
Hello Sir,
I'm still in doubt. You told that we need to check more combination if possible in this question but Candidate Key is nothing but minimal Super Key then if there are other possible then why should I try them?
For Example : In your example why should I move to using 3 values (DCH Closure) ?
Give any Counter Example to clear my doubt!
And Your teaching way is really awsome ! Thanks a lot and keep making more videos.
did you find out ?
@@anushiya4453 It's been 6 years. I don't remember now. I'm sorry
It's ok ,no problem ✌️
If we take DAH closure we would get DAH neh that time as we have already confirmed that DA is a candidate key so won't DAH WOULD BE AN CANDIDATE KEY?
If there is only D closure(i.e. D is candidate key) ,is it necessary to calculate other with D or not??
pls give a lecture on finding superkey and primary key in the same type of question discussed in video
DAG bhi to ho skta????
Why u dont have option of
Shri Bhagubhai Mafatlal Polytechnic (Mumbai) in organisation
I want to register ...
In the closure of DC, won’t G be determined by CH?
Why [DBA] cannot be a candidate key?
Also if A,B,C,D,E,F,G,H all would be present in right hand side of FDs then how to proceed?
Thank you so much for your help.
is it always on trial and error basis ? Is there a way to know how many candidate keys there are ?
sir is "DAB" not candidate ki?.......then number of candidate key will more than 4....................please clear my confusion......
Thank you! Isn't [CHAD]+ a candidate key?
I don't think [CHAD]+ is a candidate key as [DA]+ already is a candidate key, so there is no point of having a combination of another attribute with a candidate key.
***** It is, but he's trying to find the set of minimal candidate keys
***** [CHAD]+ = CHADGBF, E is not determined here
+Supratik Majumdar [AD] is already a set of candidate keys, so [CHAD] must be a set of candidate keys, the only problem here is you only need to find the minimum candidate keys.
+Naveen Kumarasinghe (නවියා)
No because by definition of candidate key, none of its subset is a candidate key...but AD is!
Awesome thank you very much
Amazing video.
But I think DEG, is also a Candidate Key.
A candidate key is the minimal super-key for a relation. Notice that DE is already a canidate key. Then any other key that has DE in it, like DEG or DEA or DEABC etc, is not a canidate key because, while it is a super-key for the relation, it is not the minimal super key
@@TheBeatles986 Thank you, I really needed that explanation
can I randomly pick any candidate key as a primary key from this set?
What if I choose DEH? as DE is a candidate key it will also be. Right?
In the same question how can I check their normalisation form?
in case all the abcdef are present somehow in right side than ? from where to start?
What about ABCDEFGH? Is that a candidate key? Are you counting only the minimal candidate keys?
how it can be 4 candidate keys only where we can also have dab dac dae daf dag and many other as candidate key!! logically dac dae dab etc are also subset of the relation attributes!! isnt it?
Dear sir ,
If suppose in place of D , D and E remain independent , will the procedure be same???
+Divyansh Bahuguna
Kindly ask any doubt on techtud.com
As the video author will be notified by email and chances of getting quich answer is very high.
Sir if on the right hand side all the attributes are present so how we will find the candidate keys
Good explanation sir
I thought that subsets of candidate keys cannot be candidate keys themselves. How does this work?
Hey great videos!
Is there any particular reason you are underlining letters as you go through the closure sets?
Thanks!
in case of [DCH], DC is coming which is already a candidate key.. so we can determine all other terms. then how come DCH is not a candidate key?
DC is not a candidate key