# Database Relational Homework help

The Issue "Think about a relation R with five characteristics ABCDE. You're because of the following dependancies

1. A->B
2. BC->E
3. Erectile dysfunction->A

List all of the secrets for R.

The teacher gave us the secrets, That are ACD,BCD,CDE

And we have to show the job to get at them.

The Very First two I solved.

For BCD, the transitive of two with 3 to obtain (BC->E)D->A => BCD->A. as well as for ACD id the the transitive of just one with 4 (BCD), to obtain (A->B)Compact disc->A => ACD->A

However I can't learn how to get CDE.

Therefore it appears Used to do it wrong, after searching I discovered this answer

1. methodology to locate secrets: consider attribute sets α that contains: a. the determinant characteristics of F (i.e. A, BC, Erectile dysfunction) and b. the characteristics NOT included in the determined ones (i.e. C,D). Then perform the attribute closure formula: if α+ superset R then α -> R Three secrets: CDE, ACD, BCD Source

From what I will tell, since C,D are this is not on the left side from the dependencies. The secrets remain sides with Compact disc pre-appended for them. Can anybody explain this in my experience in better detail why?

To obtain they secrets, starting with among the dependencies and taking advantage of inference to increase the set.

Allow me to try it out with simple British, you'll find formal definition the internet easily.

e.g. begin with 3).

``````ED -> A
``````

(knowing E and D, I understand A)

``````ED ->AB
``````

(knowing E and D, I understand A, by knowing A, I understand B too)

``````ED->AB
``````

Still, C can't be known, and I have tried personally all of the rules now except BC->E, And So I add C left hands side, i.e.

``````CDE ->AB
``````

so, by knowing C,D and E, you will be aware A and B too, Hence CDE is really a key for the relation ABCDE. You repeat exactly the same process, beginning along with other rules until exhausted.