Question

Find the candidate key of r(a,b,c,d,e,f,g,h) ,ab-c,bd-ef,ad-g,a-h

Answer 1

Answer:

this is the correct answer key

Explanation:

CANDIDATE KEYS

A candidate key of a relation schema R is a subset X of the

attributes of R with the following two properties:

1. Every attribute is functionally dependent on X,

i.e., X

+ = all attributes of R (also denoted as X

+ = R).

2. No proper subset of X has the property (1),

i.e., X is minimal with respect to the property (1).

A sub-key of R: a subset of a candidate key;

a super-key:aset of attributes containing a candidate key.

We also use the abbreviation CK to denote "candidate key".

Let R(ABCDE) be a relation schema and consider the fol-

lowing functional dependencies F = {AB → E, AD → B, B → C,

C → D}. Since

(AC)

+ =ABCDE,

A

+ = A, and

C

+ = CD,

we know that AC isacandidate key, both A and C are sub-keys,

and ABC is a super-key. The only other candidate keys are AB

and AD. Note that since nothing determines A, A is in every can-

didate key.