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⇱ Quiz about ER and Relational Models

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Question 1

Given the basic ER and relational models, which of the following is INCORRECT?

  • An attribute of an entity can have more than one value

  • An attribute of an entity can be composite

  • In a row of a relational table, an attribute can have more than one value

  • In a row of a relational table, an attribute can have exactly one value or a NULL value

Question 2

Suppose (

, B) and (

,D) are two relation schemas. Let r1 and r2 be the corresponding relation instances. B is a foreign key that refers to C in r2. If data in r1 and r2 satisfy referential integrity constraints, which of the following is ALWAYS TRUE? 

👁 DBMSGATE2012

  • A

  • B

  • C

  • D

Question 3

Consider the following relations A, B, C. How many tuples does the result of the following relational algebra expression contain? Assume that the schema of A U B is the same as that of A. 

👁 Image
 
Table A
Id Name Age
----------------
12 Arun 60
15 Shreya 24
99 Rohit 11

Table B
Id Name Age
----------------
15 Shreya 24
25 Hari 40
98 Rohit 20
99 Rohit 11

Table C
Id Phone Area
-----------------
10 2200 02 
99 2100 01

  • 7

  • 4

  • 5

  • 9

Question 4

Consider a relational table r with sufficient number of records, having attributes A1, A2,…, An and let 1 <= p <= n. Two queries Q1 and Q2 are given below.

👁 GATE2011DBMS1


The database can be configured to do ordered indexing on Ap or hashing on Ap. Which of the following statements is TRUE?

  • Ordered indexing will always outperform hashing for both queries

  • Hashing will always outperform ordered indexing for both queries

  • Hashing will outperform ordered indexing on Q1, but not on Q2

  • Hashing will outperform ordered indexing on Q2, but not on Q1.

Question 5

Which commands are used to control access over objects in relational database?

  • CASCADE & MVD

  • GRANT & REVOKE

  • QUE & QUIST

  • None of these

Question 6

If D1, D2...Dn are domains in a relational model, then the relation is a table, which is a subset of

  • D1⊕D2⊕...⊕Dn

  • D1xD2x...xDn

  • D1∪D2∪...∪Dn

  • D1∩D2∩...∩Dn

Question 7

The join operation can be defined as

  • a cartesian product of two relations followed by a selection

  • a cartesian product of two relations

  • a union of two relations followed by cartesian product of the two relations

  • a union of two relations

Question 8

The 'command' used to change contents of one database using the contents of another database by linking them on a common key field?

  • Replace

  • Join

  • Change

  • Update

Question 9

For a weak entity set to be meaningful, it must be associated with another entity set in combination with some of their attribute values, is called as:
  • Neighbour Set
  • Strong Entity Set
  • Owner Entity Set
  • Weak Set

Question 10

Drop Table cannot be used to drop a Table referenced by __________ constraint. (a)Primary key (b)Sub key (c)Super key (d)Foreign key
  • (a)
  • (a), (b) and (c)
  • (d)
  • (a) and (d)

There are 74 questions to complete.

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