Why do we have to create a primary index on a primary key
A. | Ease of searching |
B. | Sequential ordering of a file |
C. | Both (a) and (b) |
D. | None of these |
Option: C Explanation : Click on Discuss to view users comments. |
In context with relational Algebra. Which of the following are unary operatiors.
1.Select
2. Project
3. Union
4. Product
A. | 1 and 3 only |
B. | 2 and 4 only |
C. | 1 and 2 only |
D. | All are binary |
Option: C Explanation : Click on Discuss to view users comments. |
Let R is a relation schema, R(A, B, C, D) and F = {A —> B, B --> C, C —> A) is the set of functional dependency. Determine the key of relation ?
A. | A |
B. | B |
C. | C |
D. | D |
Option: D Explanation : Rule to find out the key in relation :-
Now considering these 5 points we get D as Key. Click on Discuss to view users comments. Jyoti said: (10:51am on Tuesday 22nd October 2013)
A superkey is a set of attributes whose closure contains all the attributes. A candidate key = a minimal superkey and primary key is selected candidate key here A , B , C all closure have all arttibutes(ABC) only D is left.hence we have AD,BD,CD as candidate keys and anyone of them can be a primary key
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Which of the following statement is correct?
A. | F |= x ---> x iff y ⊆ x+ |
B. | F |= y ---->x iff y ⊆ x+ |
C. | F |=x --->y iff x+ ⊆ y |
D. | F |= y --->x iff x+⊆ y |
Option: A Explanation : Click on Discuss to view users comments. |
Given the basic ER and relational model which of the following is incorrect?
A. | An entity can have more than one attrbute |
B. | An attribute of an entity can be composite. |
C. | In row of a relational table, an attribute have more than one value. |
D. | In row of a relational table, an attribute can have exactly one vlaue or a NULL value. |
Option: C Explanation : Click on Discuss to view users comments. |