PYQ – UNIT IV DBMS

Q1) Data Scrubbing is a process to upgrade the quality of data before it is moved into a data warehouse.

Q2) The active data warehouse architecture includes which of the following:

• A) At least one data mart
• B) Data that can extracted from numerous internal & external sources
• C) Near Real-time updates
• D) All of the above

Q3) Goal of data mining includes To explain some observed event or condition

Q4) A data warehouse is organized around important subject areas

Q5) What do data warehouse support?

Ans: OLAP

Q6) Which of the following are DML Statements? [June 2019]

a) UPDATE [table name] SET [Columnname]=VALUE

b) DELETE [tablename]

c) SELECT * FROM [tablename]

d) (A),(B),(C) are true

Q7) Which of the following key constraints is required for functioning of foreign key in the context of relational database?

Ans: Primary Key

Q8) In relational Database, if a relation R is in BCNF, then which of the following is true about relation?

Ans: R is in 2NF & 3NF

Q9) In relational database management which of the following is/are property/properties of candidate key?

P: Uniqueness, Q: Irreducibility

Ans: Both P & Q

Q10) Which of the following features is supported in the relational database model?

Ans: Association with multiplicities

Q11) Following table has two attributes Employee_ID & Manager_ID where Employee_ID is a primary key & Manager_ID is foreign key referencing Employee_ID with one delete cascade:

on deleting the table (20, 40) the set of other tuples that must be deleted to maintain the referential integrity of table is

Ans: (30,35) & (35, 20) only

Explanation:

If (20, 40) is deleted then the entry in manager_id containing 20 value will violate the referential integrity constraints. So entry (35, 20) is deleted because of deletion of (20, 40).

Similarly entry (30, 35) is deleted because of deletion of entry (35, 20).

Hence (30,35) & (35, 20) is Answer.

Q12) With respect to relational algebra which of the following operations are included from mathematical set theory

a) Join

b) Intersection

c) Cartisian Product

d) Project

Ans: (b) & (c)

Q13) Which of the following has same expressive power with regard to relational query language?

a) Rational algebra and domain relational calculus
b) Relational algebra and tuples relational calculus
c) Relational algebra and domain relational calculus restricted to safe expression
d) Relational algebra and tuples relational calculus restricted to safe expression
A) a and b only
B) c and d only
C) a and c only
D) b and d only