6 votes 6 votes Every table with two single-valued attributes is in 1NF, 2NF, 3NF and BCNF. ???? plz define clearly?? is it true for all the table having more than two attribute?? #refrence gate2014 Databases database-normalization + – yankur9 asked Jan 28, 2017 yankur9 2.2k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 3 votes 3 votes It will be in bcnf because bcnf says that if we have a functional dependency as A->B then A must be the Super key. So if we have only 2 attributes then definitely one will be key. So 2 possible set of functional dependency are there wither only one should be there { A->B} or this set can be there { A->b, B->A}. Now whatever the case is it will be in BCNF. Tendua answered Feb 1, 2017 selected Jan 16, 2018 by yankur9 Tendua comment Share Follow See all 4 Comments See all 4 4 Comments reply yankur9 commented Feb 1, 2017 reply Follow Share i was asking it is true for more than two attribute??? 1 votes 1 votes Tendua commented Feb 2, 2017 reply Follow Share Depends what is the functional dependency combinations 0 votes 0 votes yankur9 commented Feb 2, 2017 reply Follow Share they didn't give any functional dependency in case of two attribute but it was in BCNF i simply asked if there is no functional dependency given in case of more than two attribute whether it is in bcnf or not?? 1 votes 1 votes rishu_darkshadow commented Sep 18, 2017 reply Follow Share i was asking it is true for more than two attribute??? No, it is not always true.. it is totally depends upon given FD 1 votes 1 votes Please log in or register to add a comment.
2 votes 2 votes It is true for any dependency in case of 2 attributes but in case of more than 2, it depends upon the FDs. Purvi Agrawal answered Mar 11, 2017 Purvi Agrawal comment Share Follow See all 0 reply Please log in or register to add a comment.
2 votes 2 votes I discussed this question with my teacher. It's false for more than two attributes. only two attributes which are single valued : TRUE two single valued attributes : False Karan Saini answered Jul 19, 2017 Karan Saini comment Share Follow See all 0 reply Please log in or register to add a comment.
2 votes 2 votes For a table with two single valued attributes, it is always true. For the table with more than two single valued attributes, it depends on given functional dependencies. So we can say it's not always true for this case. smsubham answered Aug 16, 2017 smsubham comment Share Follow See all 2 Comments See all 2 2 Comments reply yankur9 commented Aug 20, 2017 reply Follow Share i want to know in case of more than two attribute . if there is no functional dependency given. is it in bcnf?? because in case of two attribute , if there is no functional dependency given. it will always be in bcnf 1 votes 1 votes smsubham commented Aug 21, 2017 i edited by smsubham Aug 21, 2017 reply Follow Share Here you should understand why for 2 attribute its always in BCNF. Suppose we have R(AB) What are the non-trivial dependency possible A-> B , B -> A If we take any combination of these FD it will be in BCNF as LHS is always super key. Now let's see for more than 2 attributes. R(ABC) A -> B, A -> C , B -> C , B-> A , AB -> C , BC -> A , AC -> B let's say we take A -> B and B -> C CK is A. Prime attributes is A and non-prime are B and C. So B -> C is a transitive dependency. ( not prime to nonprime) So it fails even 3NF. Similarly, in some cases, it may even fail 2 NF, so there is no point is talking about BCNF. Hope this helps. 3 votes 3 votes Please log in or register to add a comment.