Step by step explanation on how to find the decomposition of a relation to BCNF. #BCNF #Decimposition #NormalForm #Data #dbms Please subscribe to my channel / @csds-computerdatascie...
No cap, after searching and listening all BCNF videos on RU-vid for DBMS finals this video is BEST VIDEO for BCNF. If you see this please dont skip this gem video. Thank you so much man, amazing explonation 🙏👌💯
gj that was very well explained and good sheets instandly understood, damn its hard to find good explaining videos but when youve found one youre happy and i am now ty man
For Canditate Keys for something like R4 lets say you end up with something like (A, C, F, G, E) would that be ACF->GE or AC->FGE or would it be ACFG->E, I was a bit of confused did this arrow just need to be true for the functional dependencies given in the problem I was working on?
Candidate keys are defined by the known functional dependencies. The candidate key for (A,C,F,G,E) would be the minimum amount of attributes that there closure has all the attributes of the relation (A,C,F,G,E)
FDs A->C and B->D have attributes that depend on part of the candidate key, so this relationship is not even in 2NF, let alone 3NF. So, how can you proceed with BCNF decomposition if it is not 3NF?
@@martinlunn9660 I think you are mistaken. BCNF is a subset of 3NF which in turn is a subset of 2NF. To decompose to BCNF, the FDs need to be in 3NF. Do not forget that FDs are describing a database schema so "relation doesn't need to be in any specific form to be decomposed' is invalid since you are not decomposing relations, but rather database schemas.
@@user-xg9ft7fs4i Strictly speaking, a relation doesn't need to be in 2NF to apply BCNF decomposition. However, it is more common to first ensure that a relation is in 2NF before moving on to decompose it into BCNF, as the process of normalization typically follows a step-by-step progression from 1NF to 2NF to 3NF and then to BCNF. If you decompose a relation directly into BCNF, it will automatically satisfy the requirements of 2NF (and 3NF) as well. This is because BCNF is a stronger normal form than 2NF and 3NF.
In this case, we use the functional dependency F->F, because F can be determined from itself. The rest of the decomposition is according to the steps in the video.
C & D are not in the partial relation R6, therefore the relation AB-> CD is not present in the relation R6. In each partial relation we are looking for the relevant functional dependencies, and in R6 this is only AB->AB.
{D}⁺- is the closure of the attribute D. The plus sign refers to the closure. If the term closure isn't familiar, I suggest checking out my video on the closure of an attribute. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RW17jm9hR4w.html
