1. What is meant by Proactive, Retroactive and Simultaneous Update.

Proactive Update :  The updates that are applied to database before it becomes effective in real world .

Retroactive Update :  The updates that are applied to database after it becomes effective in real world .

Simulatneous Update :  The updates that are applied to database at the same time when it becomes effective in real world .

2. What do you understand by dependency preservation?

Given a relation R and a set of FDs F, dependency preservation states that the closure of the union of the projection of F on each decomposed relation Ri is equal to the closure of F. i.e.,

((PR1(F)) U … U (PRn(F)))+ = F+

if decomposition is not dependency preserving, then some dependency is lost in the decomposition.

3. A B C is a set of attributes. The functional dependency is as follows

AB -> B
AC -> C
C -> B

a) is in 1NF
b) is in 2NF
c) is in 3NF
d) is in BCNF

Answer :  (a) is in 1NF since (AC)+ = { A, B, C} hence AC is the primary key. Since C B is a FD given, where neither C is a Key nor B is a prime attribute, this it is not in 3NF. Further B is not functionally dependent on key AC thus it is not in 2NF. Thus the given FDs is in 1NF.

4. What is Authorization and Integrity manager?

It is the program module, which tests for the satisfaction of integrity constraint and checks the authority of user to access data.

5. A dominant entity is the entity

a) on the N side in a 1 : N relationship
b) on the 1 side in a 1 : N relationship
c) on either side in a 1 : 1 relationship
d) nothing to do with 1 : 1 or 1 : N relationship

Answer :  (b) on the 1 side in a 1 : N relationship

6. In mapping of ERD to DFD

a) entities in ERD should correspond to an existing entity/store in DFD
b) entity in DFD is converted to attributes of an entity in ERD
c) relations in ERD has 1 to 1 correspondence to processes in DFD
d) relationships in ERD has 1 to 1 correspondence to flows in DFD

Answer :  (a) entities in ERD should correspond to an existing entity/store in DFD

7. Select 'NORTH', CUSTOMER From CUST_DTLS Where REGION = 'N' Order By
CUSTOMER Union Select 'EAST', CUSTOMER From CUST_DTLS Where REGION = 'E' Order By CUSTOMER

The above is

a) Not an error
b) Error - the string in single quotes 'NORTH' and 'SOUTH'
c) Error - the string should be in double quotes
d) Error - ORDER BY clause

Answer :  (d) Error - the ORDER BY clause. Since ORDER BY clause cannot be used in UNIONS