Objective: this assignment is designed to let you have a hands-on experience wit
ID: 3806853 • Letter: O
Question
Objective: this assignment is designed to let you have a hands-on experience with normalization A normalized schema provides a good starting point for further development of a database application and easier maintenance it later on. Normalization is a process of modifying an existing database schema to bring its component tables into compliance with a series of normal forms. The goal of the normalization is to ensure that every non-key attribute in every table is directly dependent on the whole candidate key (nothing else but the key). Consider a relation R with six attributes A, B, C, D, E, F. You are given the following dependences: C rightarrow F, E BC rightarrow D D rightarrow B, and ED rightarrow C Is {(ABDE)} a candidate key of this relation? If not, is {(ADE)}? Justify your answer. Consider the relation F with six attributes F, R I, D, A, Y with the following dependences: R rightarrow I RY rightarrow F FY rightarrow A, and FA rightarrow R a) List all keys for F and justify your answer. b) Identify prime and non-prime attributes and justify your answer. c) Classify each function dependency and justify your answer. d) Determine normal form for the relation F and justify your answer.Explanation / Answer
Ans 1.
a candidate key is a "minimal" super key which can identify uniquely a tuple in a relation.
so,in the given question
if we consider (ABCDE) as a key and try to find out the closure of this we will get the whole relation.
also if we consider (ADE) as a key and try to find out the closure we will get the whole relation,but to get all the attributes we here needed only three attributes(minimum possible attributes).
so it is in the "minimal" form.
hence (ADE) is the candidate key through we can obtain all other atrributes and (ABCDE) can become the Super key but not the candidate key .
Ans.2(a)
If we find out closures of all the relation given for the relation F,
we can check that on taking closure of (FYR) we can get all other attributes shown in the dependencies
So, (FYRD) taken together as key can yield the attributes in the dependencies
hence (FYRD) is a candidate key(minimal).(since D is not there in dependencies so we have to take that to get whole relation)
It can be also considered as "primary key".(can also uniquly identify tuples)
and taking (FYARD) we can get all the attributes so it is a super key.
other closures can not yield all the attributes isolately.
(b)
Since (FYRD) is a candidate key, so all the attributes in this are prime attributes and all other are non prime attributes{A,I}.
(c)As (FYRD) is candidate key,so dependency from R to I is "partial function dependency"(since 'R' being prime attribute(part of full key) depends on non prime attribute I)
dependency from FY to A is whole function dependency.
(d)Given relation is in first normal form(1NF) it has the primary key and no repeated datas and due to presence of partial function dependency(R->I) it is not in Second normal form(2NF).
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.