Relational database management systems mcq quiz with answers 19

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MCQ on various aspects in DBMS including database schedules, indexing, data storage, normalization, database views, query optimizers and multivalued dependency questions with answers, RDBMS Multiple Choice Questions with Answers

Database management systems - MCQ exam questions

 

1. An attribute that can be subdivided into sub-attributes is called

(a) composite attribute
(b) derived attribute
(c) multi-valued attribute
(d) stored attribute

Answer: (a) composite attribute

Composite attribute can be divided into meaningful sub-attributes (e.g., Student_Name → First_Name, Last_Name). Example: Student_Name can be a composite attribute with components Student_First_Name and Student_Last_Name sub-attributes.

2. __________ cannot accept NULL values.

(a) candidate key
(b) foreign key
(c) primary key
(d) unique attribute

Answer: (c) Primary key

Primary key enforces UNIQUE + NOT NULL constraints.

3. An attribute of a table that links the primary key of another table is called

(a) candidate key
(b) composite key
(c) foreign key
(d) none of these

Answer: (c) Foreign key

Foreign key is an attribute that references the primary key or unique attribute of another table.

4. How do we refer all candidate keys other than the primary key?

(a) alternate keys
(b) foreign keys
(c) super keys
(d) none of these

Answer: (a) alternate keys

Candidate keys except the primary key are called alternate keys.

5. DCL commands are

(a) create and drop
(b) insert and delete
(c) grant and revoke
(d) select and update

Answer: (c) grant and revoke

GRANT and REVOKE commands are part of Data Control Language (DCL). They are used to grant and revoke access privileges (select, insert, delete, update, create, etc.) to different database users on various database components.

6. An operation that produces a temporary relation when performed on a relation is

(a) intersection
(b) join
(c) selection
(d) projection

Answer: (d) projection

Projection creates a temporary relation with selected attributes.

Project is a relational algebra operation that refers to the creation of a relation (temporary) by selecting set of attributes from another relation (or an expression).

7. If a relation is in __________, it is also in 3NF.

(a) 2NF
(b) BCNF
(c) both (a) and (b)
(d) none of these

Answer: (b) BCNF

Every BCNF relation is also in 3NF.

8. “Every determinant is a key” is a property of

(a) 2NF
(b) 3NF
(c) BCNF
(d) 4NF

Answer: (c) BCNF

A relation with set of functional dependencies where every determinant (LHS attribute(s)) is a key is said to be in Boyce-Codd Normal Form (BCNF).

9. A virtual relation visible to users is called

(a) relation
(b) tuple
(c) cardinality
(d) view

Answer: (d) view

A view is simply any SELECT query that has been given a name and saved in the database. For this reason, a view is sometimes called a named query or a stored query. To create a view, you use the SQL syntax:

        CREATE OR REPLACE VIEW <view_name> AS

        SELECT <any valid select query>;

10. Index associated with a sorted data file is

(a) multi-level index
(b) primary index
(c) secondary index
(d) none

Answer: (b) primary index

Index on Sequential File, also called Primary Index, when the Index is associated to a Data File which is in turn sorted with respect to the search key.

• A Primary Index forces a sequential file organization on the data file;
• Since a data file can have just one order there can be just one Primary Index for data file.

11. Rollback for a transaction is used to

(a) delete the transaction
(b) recover from failure
(c) restore old transaction
(d) update transaction

Answer: (c) restore the old transaction

Rollback will undo all the updates performed by an old transaction to restore that transaction to an old consistent state.

12. Serializability is ensured by

(a) locking
(b) time-stamping
(c) both of these
(d) none

Answer: (c) both of these

Both locking and time-stamping protocols are used for ensuring seriablizability.

13. Cardinality ratio is

(a) number of entities
(b) entities related via relationship
(c) number of attributes
(d) rows/columns ratio

Answer: (b)

Cardinality ratio, (also called as, type of relationship) is the number of entities in one entity set that are related to number of entities in another entity set via a relationship set.

They are one-to-one, one-to-many, many-to-one, and many-to-many.

14. Permanently remove all data from PILOT table

(a) DELETE ALL FROM PILOT
(b) DELETE FROM PILOT
(c) DROP ALL FROM PILOT
(d) DROP FROM PILOT

Answer: (b) DELETE FROM PILOT

15. Undo effects of an aborted transaction

(a) redo transaction
(b) commit
(c) rollback
(d) savepoint

Answer: (c) rollback

Rollback will undo all the updates performed by an old transaction to restore the transaction to an old consistent state.

 

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