If a database table is in Boyce-Codd normal form, it is alsoin a. the first norm

Question

If a database table is in Boyce-Codd normal form, it is alsoin

a.     the first normalform.                                b. the second normal form.

c.     the third normalform.                              d. all of a., b., and c.

Explanation / Answer

the database table is in 1NF if the domain of each attribute of thetable is atomic,i.e. only one value is associate with eachattribute and this value is not a set of values or alist ofvalues. the database table is in 2NF if it is in 1NF and if all non-primeattributes are fully functional dependent on the keys. non-prime attributes are those that are not the part of anycandidate keys.An FD X->Y is Fully functional dependent on X ifthere is no proper subset Z of X such that Z->Y and X->Y isleft reduced.2NF doesn't allow partial dependency. the database table is in 3NF if it is in 2NF and contain no trivialdependencies.in other way a table is in 3NF if for all non-trivialFDs in F+(Closure of Fds) of the form X->A,either X is aSuperkey or A is a prime attribute. in BCNF: for every X->Y in F+, either X->Y is trivial FD or X is the super key of table.thismeans only non-trivial FDs allow in BCNF are thos FDs whosedeterminants are candidate keys. we can differintiate 3NF and BCNF as follows: 1.if Y is a prime attribute ,X must be superkey to attain BCNF. 2.in 3NF x doesn't have to be superkey,but in this case Y must beprime attribute.    hence we can Say that BCNF is more restricted than3NF,    the (d) option is correct.

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