Third Normal Form (3NF) | Database Normalization | DBMS

hello friends and welcome to sty tonight see YouTube channel in this video we will talk about the third normal form if you're following a normalization videos from starting then you must have already seen the videos for the first and the second normal forms if not I suggest you to watch those videos before starting with this one in the last video we learned about the second normal form and even normalized our score table into the second normal form for a quick recap we had three tables student subject and score following word the primary keys score table had teachers name which was only dependent on subject so we moved it to the subject table hence now the score table is normalized to the second normal form but we missed to add some information in the score table in our last video we need to save exam name and total marks also in the score table so should we just add them in the score table let's do it so here is our updated score table so coming back to the third normal form for a table or a relationship to be in third normal form it must be in the second normal form and it should not have transitive dependency remember partial dependency this time it's transitive dependency that different to understand what partial dependency is once and for all watch your video for the second normal form so what is transitive dependency with exam name and total marks fields our school table now looks like this primary key for our school table is a composite key which means it's made up of two attributes or columns student ID plus subject ID as we can see our new column exam name depends on student and subject for example a mechanical engineering student will have workshop exam but a computer science student pooned and for some subjects you have practical exams and for some you don't so we can say that exam name depends on student and subject both and a second new column total marks does it depend on student or subject or marks or the new column exam name well total marks depends on exam name you must be thinking how in our colleges practical exams are generally of 40 marks or 30 marks and theory exams are for 70 or 60 marks session ELLs are of around 4050 marks so all in all total marks changes based on exam hence we can say that total marks depends upon the exam name now in our table we already know that the primary key is student ID plus subject ID and all other columns or attributes depends on it except total marks which depends on exam name but exam name is not a part of a primary key right this is transitive dependency when there is an attribute in a table which depends on some non-prime attribute and not on the prime attributes and the solution to this problem is take exam name and total marks and put them in an exam table and use exam ID wherever required so now a school table is storing more information and it is in the third normal form [Applause] hope you like this video and I hope that now you understand the third normal form in a better way don't forget to share this video with your friends and colleagues and if you haven't subscribed to our channel yet please do subscribe to our Channel [Music]

Channel: Studytonight with Abhishek

Views: 865,177

Keywords: database normalisation, 3rd Normal form, third normal form, transitive dependency, what is transitive dependency, what is normalisation, DB normalization, 3NF, normalizing table, dbms 3rd normal form, 3rd normal form dbms, dbms tutorial video, RDBMS normalization, 1Nf, 2NF, BCNF

Id: aAx_JoEDXQA

Length: 4min 15sec (255 seconds)

Published: Thu Feb 08 2018