## ER-Model

 Question 1

In an Entity-Relationship (ER) model, suppose R is a many-to-one relationship from entity set E1 to entity set E2. Assume that E1 and E2 participate totally in R and that the cardinality of E1 is greater than the cardinality of E2.

Which one of the following is true about R?

 A Every entity in E1 is associated with exactly one entity in E2. B Some entity in E1 is associated with more than one entity in E2. C Every entity in E2 is associated with exactly one entity in E1. D Every entity in E2 is associated with at most one entity in E1.
Database-Management-System       ER-Model       GATE 2018
Question 1 Explanation:

The M : 1 relationship holds between two entities E1 and E2, in which each tuple from E2 is in relation with many tuples of E1. One tuple from E1 is in relation with only one tuple of E2. It is given that participation from both the sides is total and the cardinality of E1 is greater than E2.

Therefore, every entity E1 is associated with exactly one entity in E2.
 Question 2

An ER model of a database consists of entity types A and B. These are connected by a relationship R which does not have its own attribute. Under which one of the following conditions, can the relational table for R be merged with that of A?

 A Relationship R is one-to-many and the participation of A in R is total. B Relationship R is one-to-many and the participation of A in R is partial. C Relationship R is many-to-one and the participation of A in R is total. D Relationship R is one-to-many and the participation of A in R is partial.
Database-Management-System       ER-Model       GATE 2017 [Set-2]
Question 2 Explanation:

The relational table for R be merged that of A, if the relationship R is Many-to-one and the participation of A in R is total.
 Question 3

Consider an Entity-Relationship (ER) model in which entity sets E1 and E2 are connected by an m:n relationship R12, E1 and E3 are connected by a 1:n (1 on the side of E1 and n on the side of E3) relationship R13.

E1 has two single-valued attributes a11 and a12 of which a11 is the key attribute. E2 has two single-valued attributes a21 and a22 is the key attribute. E3 has two single-valued attributes a31 and a32 of which a31 is the key attribute. The relationships do not have any attributes.

If a relational model is derived from the above ER model, then the minimum number of relations that would be generated if all the relations are in 3NF is ___________.

 A 4 B 6 C 7 D 8
Database-Management-System       ER-Model       GATE 2015 [Set-1]
Question 3 Explanation:

 Question 4

What is the optimized version of the relation algebra expression πA1A2F1F2(r)))), where A1, A2 are sets of attributes in  with A1 ⊂ A2 and F1, F2 are Boolean expressions based on the attributes in r?

 A πA1 (σ(F1∧F2) (r)) B πA1 (σ(F1∨F2) (r)) C πA2 (σ(F1∧F2) (r)) D πA2 (σ(F1∨F2) (r))
Database-Management-System       ER-Model       GATE 2014 [Set-3]
Question 4 Explanation:
 Since A1 ⊂ A2 will get only attribute A1 as it is in the outside. So we can remove project A2.
 Two Selects with Boolean expression can be combined into one select with AND of two Boolean expressions.
 Question 5

A prime attribute of a relation scheme is an attribute that appears

 A in all candidate keys of R. B in some candidate key of R. C in a foreign key of R. D only in the primary key of R .
Database-Management-System       ER-Model       GATE 2014 [Set-3]
Question 5 Explanation:
A prime attribute of a relation scheme R is an attribute that appears in some candidate keys of R. Need not to appear in all the candidate keys.
Ex: AB, BC, CD are candidate keys of R(ABCD). In the FDs set one attribute may not be part of all the FDs.
 Question 6

Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee. Assume that every employee has at least one associated dependent in the dependent relation.

```employee (empId, empName, empAge)
dependent(depId, eId, depName, depAge)```

Consider the following relational algebra query:

`∏empId(employee)-∏empId(employee⋈(empId = eID)∧(empAge ≤ depAge)dependent)`

The above query evaluates to the set of empIds of employees whose age is greater than that of

 A some dependent. B all dependents. C some of his/her dependents. D all of his/her dependents.
Database-Management-System       ER-Model       GATE 2014 [Set-3]
Question 6 Explanation:
The inner query selects the employees whose age is less than or equal to at least one of his dependents. So, subtracting from the set of employees, gives employees whose age is greater than all of his dependents.
 Question 7

Consider the following relation schema

Students(rollno: integer, sname: string)
Courses(courseno: integer, cname: string)
Registration(rollno: integer, courseno: integer, percent: real)

Which of the following queries are equivalent to this query in English?

`"Find the distinct names of all students who score more than 90% in the course numbered 107" `
```(I) SELECT DISTINCT S.sname
FROM Students as S,Registration as R
WHERE R.rollno = S.roll AND R.courseno = 107 AND R.percent > 90
(II) Πsname(σcourseno=107∧percent>90(Registration ⋈ Students))
(III) {T|∃S ∈ Students, ∃R ∈ Registration (S.rollno = R.rollno ∧ R.courseno = 107 ∧ R.percent > 90 ∧ T.sname = S.sname)}
(IV) {〈SN〉|∃SR∃RP(〈SR,SN〉 ∈ Students ∧ 〈SR,107,RP〉 ∈ Registration ∧ RP>90)}
```
 A I, II, III and IV B I, II and III only C I, II and IV only D II, III and IV only
Database-Management-System       ER-Model       GATE 2013
Question 7 Explanation:
Four queries given in SQL, RA, TRC and DRC and all four statements will retrieve the required information.
 Question 8

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

 A An attribute of an entity can have more than one value B An attribute of an entity can be composite C In a row of a relational table, an attribute can have more than one value D In a row of a relational table, an attribute can have exactly one value or a NULL value
Database-Management-System       ER-Model       GATE 2012
Question 8 Explanation:
Option (A): In ER-model, multivalued attribute of an entity can have more than one value.
Option (B): In ER model, the attribute which can be further broken down into some other attributes is called composite attribute.
Option (C): In Relational model, the intersection of one row and column should contain only one value. So, option (C) is INCORRECT.
Option (D): In Relational model, the intersection of one row and column should contain either exactly one value or NULL.
 Question 9

Consider the following ER diagram

The minimum number of tables needed to represent M, N, P, R1, R2 is

 A 2 B 3 C 4 D 5
Database-Management-System       ER-Model       GATE 2008
Question 9 Explanation:
➝ M, P are entities so they require individual tables.
➝ Here N is a Weak entity, but it need to modify the primary key of P such as P1
M = {M1, M2, M3, P1}
P = {P1, P2}
N = {N1, N2, P1}
➝ Relationship set has its own attribute, then no need to create a separate table.
➝ Finally we require 3 minimum tables to represent M, P, N, R1, R2.
 Question 10

Consider the following ER diagram

Which of the following is a correct attribute set for one of the tables for the correct answer to the above question?

 A {M1, M2, M3, P1} B {M1, P1, N1, N2} C {M1, P1, N1} D {M1, P1}
Database-Management-System       ER-Model       GATE 2008
Question 10 Explanation:
Possible set of attributes is
For M = {M1, M2, M3, P1}
P = {P1, P2}
N = {N1, N2, P1}
 Question 11

Let E1 and E2 be two entities in an E/R diagram with simple single-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. R1 and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model?

 A 2 B 3 C 4 D 5
Computer-Networks       ER-Model       GATE 2005
Question 11 Explanation:
R1 and R2 two relationships between E1 and E2.
R1 is one to many.
R2 is many to many.
→ E1 and E2 have separate table because they need to store multiple values.
→ R2 also have separate table by considering Primary keys E1 and E2 as foreign keys.
→ R1 is converted to many side table i.e., E2 as Primary key and E1 as Foreign key.
So, totally we need 3 tables to store the value.
 Question 12

Which one of the following is used to represent the supporting many-one relationships of a weak entity set in an entity-relationship diagram?

 A Ovals that contain underlined identifiers B Rectangles with double/bold border C Diamonds with double/bold border D Ovals with double/bold border
Database-Management-System       ER-Model       GATE 2020
Question 12 Explanation:
An entity set that does not have sufficient attributes to form a primary key is termed as a weak entity and an entity set that has a primary key is termed as strong entity set. For a weak entity set to be meaningful, it must be associated with another entity set, called identifying or owner entity set. The relationship associating the weak entity set with the identifying entity set is called the identifying relationship and it is represented by double diamond. The identifying relationship is many-to-one from the weak entity set to the identifying entity set and the participation of weak entity set in the relationship is total.
 Question 13

Consider the entities 'hotel room', and 'person' with a many to many relationship 'lodging' as shown below:

If we wish to store information about the rent payment to be made by person (s) occupying different hotel rooms, then this information should appear as an attribute of

 A Person B Hotel Room C Lodging D None of theseThe information should appear as an attribute of lodging, because this is the only common attribute that relating to the hotel room and person. The information should appear as an attribute of lodging, because this is the only common attribute that relating to the hotel room and person.
Database-Management-System       ER-Model       GATE 2005-IT
Question 13 Explanation:
The information should appear as an attribute of lodging, because this is the only common attribute that relating to the hotel room and person.
 Question 14

In a schema with attributes A, B, C, D and E following set of functional dependencies are given

```A → B
A → C
CD → E
B → D
E → A ```
Which of the following functional dependencies is NOT implied by the above set?

 A CD → AC B BD → CD C BC → CD D AC → BC
Database-Management-System       ER-Model       GATE 2005-IT
Question 14 Explanation:
Apply membership test for all the functional dependencies.
Option (B):
BD → CD
BD+ = BD
i.e., BD cannot derive CD and hence is not implied.
 Question 15

Consider the following entity relationship diagram (ERD), where two entities E1 and E2 have a relation R of cardinality 1 : m.

The attributes of E1 are A11, A12 and A13 where A11 is the key attribute. The attributes of E2 are A21, A22 and A23 where A21 is the key attribute and A23 is a multi-valued attribute. Relation R does not have any attribute. A relational database containing minimum number of tables with each table satisfying the requirements of the third normal form (3NF) is designed from the above ERD. The number of tables in the database is

 A 2 B 3 C 5 D 4
Database-Management-System       ER-Model       GATE 2004-IT
Question 15 Explanation:
One table for E1, two tables for E2 (A21, A22 and A21, A23) because we need to make a separate table for multivalued attribute to satisfy minimum 1NF condition that requires atomic attributes.
Then, we get
T1: {A11, A12, A13} - key is A11
T2: {A21, A22, A11} - key is A21
T3: {A21, A23} - key is {A21, A23}
 Question 16

Consider two tables in a relational database with columns and rows as follows:

```Table: Student
ROLL_NO	  NAME	DEPT_ID
1	  ABC	   1
2	  DEF	   1
3	  GHI	   2
4	  JKL	   3
Table: Department
DEPT_ID	DEPT_NAME
1	   A
2	   B
3	   C ```
Roll_no is the primary key of the Student table, Dept_id is the primary key of the Department table and Student.Dept_id is a foreign key from Department.Dept_id.
What will happen if we try to execute the following two SQL statements?
```(i)  update Student set Dept_id = Null
where Roll_on = 1
(ii) update Department set Dept_id = Null
where Dept_id = 1 ```

 A Both (i) and (ii) will fail B (i) will fail but (ii) will succeed C (i) will succeed but (ii) will fail D Both (i) and (ii) will succeed
Database-Management-System       ER-Model       GATE 2004-IT
Question 16 Explanation:
Here in (i), when we update in Student table, Dept_id = Null, then it will not cause any problem to referenced table.
But in (ii) if we set in Department table, Dept_id = Null, then it will produce inconsistency because in Student table we will still have the tuples containing the Dept_id = 1.
 Question 17
In E-R model, Y is the dominant entity and X is a subordinate entity
 A If X is deleted, then Y is also deleted B If Y is deleted, then X is also deleted C If Y is deleted, then X is not deleted D None of the above
Database-Management-System       ER-Model       ISRO-2018
Question 17 Explanation:
→ It is the best example of referential integrity. In referential integrity, we are using a foreign key.
→ If we want to delete any entity in the dominant entity(Like primary key of a table) then subordinate entity(derived attribute) also deleted.
Note: If we want to delete any subordinate entity in entity then the dominant entity is not going to delete.
 Question 18
Which symbol denote derived attributes in the ER Model?
 A Double ellipse B Dashed ellipse C Squared ellipse D An ellipse with attribute name underlined
Database-Management-System       ER-Model       ISRO-2017 May
Question 18 Explanation:
Derived attributes are depicted by dashed ellipse.
Example:

 Question 19
Purpose of ‘Foreign Key’ in a table is to ensure
 A Null Integrity B Referential Integrity C Domain Integrity D Null and Domain Integrity
Database-Management-System       ER-Model       ISRO CS 2009
Question 19 Explanation:
A foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table or the same table.
In simpler words, the foreign key is defined in a second table, but it refers to the primary key or a unique key in the first table.
For example, a table called Employees has a primary key called employee_id.
Another table called Employee Details has a foreign key which references employee_id in order to uniquely identify the relationship between the two tables.
 Question 20
Which type of DBMS provides support for maintaining several versions of the same entity?
 A Relational Database Management System B Hierarchical C Object Oriented Database Management System D Network
Database-Management-System       ER-Model       ISRO CS 2011
Question 20 Explanation:
Many object databases, for example Gemstone or VOSS, offer support for versioning.
An object can be viewed as the set of all its versions.
Object versions can be treated as objects in their own right. Some object databases also provide systematic support for triggers and constraints which are the basis of active databases.
 Question 21

Relations produced from E-R Model will always be in

 A 1 NF B 2 NF C 3 NF D 4 NF
Database-Management-System       ER-Model       UGC-NET CS 2018 JUNE Paper-2
Question 21 Explanation:
Relations produced from E-R Model will always be in 3NF.
 Question 22
An object can have which of the following multiplicities?
 A Zero B More than one C One D All of the above
Database-Management-System       ER-Model       Nielit Scientist-B IT 4-12-2016
Question 22 Explanation:
Multiplicity is a definition of cardinality - i.e. number of elements of some collection of elements by providing an inclusive interval of non-negative integers to specify the allowable number of instances of described element. Multiplicity interval has some lower bound and (possibly infinite) upper bound
 Question 23
Bounded minimization is a technique for
 A Proving whether a promotivate recursive function is turing computable or not B Proving whether a primitive recursive function is a total function or not C generating primitive recursive functions D generating partial recursive functions
Database-Management-System       ER-Model       Nielit Scientist-B CS 2016 march
Question 23 Explanation:
● Primitive recursive functions are a class of functions that are defined using composition and primitive recursion – described below – as central operations. They are a strict subset of those μ-recursive functions (also called partial recursive functions) which are also total functions. Primitive recursive functions form an important building block on the way to a full formalization of computability.
● Most of the functions normally studied in ​ number theory​ are primitive recursive.
 Question 24
Consider the following Relationship Entity Diagram(ERD)

Which of the following possible relations will not hold if the above ERD is mapped into a relation model?
 A Person (NID, Name) B Qualification (NID, ExamID, QualifiedDate) C Exam (ExamID, NID, ExamName) D Exam (ExamID, ExamName)
Database-Management-System       ER-Model       ISRO CS 2015
Question 24 Explanation:
Given diagram is ER diagram , So any object, for example, entities, attributes of an entity, relationship sets, and attributes of relationship sets, can be represented with the help of an ER diagram.
We need to convert ER diagram to relational model.
There are two entities in the ER diagram named Person and Exam with attributes which are represented in ellipse.
Table name: Person

Now Create table for a relationship
Add the primary keys of all participating Entities as fields of table with their respective data types.
If relationship has any attribute, add each attribute as field of table.
Declare a primary key composing all the primary keys of participating entities.
Declare all foreign key constraints.
Table for “Qualification” relationship

 Question 25
E-R model uses this symbol to represent weak entity set?
 A Dotted rectangle B Diamond C Doubly outlined rectangle D None of these
Database-Management-System       ER-Model       Nielit Scientific Assistance CS 15-10-2017
Question 25 Explanation:
→ A weak entity is an entity that cannot be uniquely identified by its attributes alone.
→ It must use a foreign key in conjunction with its attributes to create a primary key.
→ The foreign key is typically a primary key of an entity it is related to.
 Question 26
Choose the correct statements
 A A total recursive function is also a partial recursive function B A partial recursive function is also a total recursive function C A partial recursive function is also a primitive recursive function D None of the above
Database-Management-System       ER-Model       Nielit Scientific Assistance CS 15-10-2017
Question 26 Explanation:
→ Primitive recursive functions are a class of functions that are defined using composition and primitive recursion
→ They are a strict subset of those μ-recursive functions (also called partial recursive functions) which are also total functions.
→ Primitive recursive functions form an important building block on the way to a full formalization of computability.
→ A total recursive function is also a partial recursive function
 Question 27
A program is a/an____ entity
 A Active B Passive C Dormant D Hyperactive
Database-Management-System       ER-Model       KVS DEC-2013
Question 27 Explanation:
→ A process is more than a program code. A process is an 'active' entity as oppose to program which consider to be a 'passive' entity.
→ Being a passive, a program is only a part of proces​ s
 Question 28
The following diagram depicts
 A Two-level model B Many to one model C One to one model D Many to many model
Database-Management-System       ER-Model       KVS DEC-2013
Question 28 Explanation:
→ The many to many model multiplexes any number of user threads onto an equal or smaller number of kernel threads, combining the best features of the one-to-one and many-to-one models.
 Question 29
An entity set that does not have sufficient attribute to form a key is termed as:
 A Primary entity set B Strong entity set C Weak entity set D Simple entity set
Database-Management-System       ER-Model       KVS DEC-2017
Question 29 Explanation:
→ An entity set that does not have sufficient attribute to form a key is termed as weak entity set.
→ It means a relation(or table) doesn’t have primary key. We are calling that relation is weak entity set.
 Question 30
Let M and N be two entities in an E-R diagram with simple single value attributes.
R​ 1​ and R​ 2​ are two relationship between M and N, where as
R​ 1​ is one-to-many and R​ 2​ is many-to-many.
The minimum number of tables required to represent M, N, R​ 1​ and R​ 2​ in the relational model are _______.
 A 4 B 6 C 7 D 3
Database-Management-System       ER-Model       UGC NET CS 2017 Jan -paper-2
Question 30 Explanation:
R​ 1​ and R​ 2​ two relationships between M and N
R​ 1​ is one to many.
R​ 2​ is many to many.
→ M and N have separate table because they need to store multiple values.
→ R​ 2​ also have separate table by considering Primary keys M and N as foreign keys.
→ R​ 1​ is converted to many side table i.e., N as Primary key and M as Foreign key.
So, totally we need 3 tables to store the value.
 Question 31
Consider the following Entity-Relationship (E-R) diagram and three possible relationship sets (I, II and III) for this E-R diagram:

If different symbols stand for different values (e.g., t​1​ is definitely not equal to t​2 ) ​, then which of the above could not be the relationship set for the E-R diagram ?
 A I only B I and II only C II only D I, II and III
Database-Management-System       ER-Model       UGC NET CS 2016 Aug- paper-2
Question 31 Explanation:
In the given E-R diagram there is Many-To-Many relationship between entity P and Q it means single value in P can relate to Multiple values in Q and vice-versa. And there is One-To-One relationship between S and T it means single value in S can relate to single value in T and vice-versa .
In table1:​ there is One to many relationship between S and T because "s1" in S attribute related with two values "t1" and "t2" in T attribute. so this table is violating One-to-One relationship of S and T as shown in E-R diagram so it can't be the relationship set of given E-R diagram.
In Table 2:​ There is one to one relationship between S and T and In P and Q also many-to many relationship constraints are not violated. So it could be the relationship set of given E-R diagram.
In Table 3:​ "p1" in P attribute is related with two values in Q attribute so many to many relationship constraints are not violate here and S and T attributes are also obeying one-to-one relationship constraints. So it could be the relationship set of given E-R diagram.
 Question 32
Which of the following provides the best description of an entity type?
 A A specific concrete object with a defined set of processes (e.g. Jatin with diabetes) B A value given to a particular attribute (e.g. height - 230 cm) C A thing that we wish to collect data about zero or more, possibly real world examples of it may exist D A template for a group of things with the same set of characteristics that may exist in the real world
Database-Management-System       ER-Model       UGC NET CS 2015 Dec- paper-2
Question 32 Explanation:
A template for a group of things with the same set of characteristics that may exist in the real world is best description of entity type.
Except option-D, remaining specifying their attributes.
 Question 33
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:
 A Neighbour Set B Strong Entity Set C Owner Entity Set D Weak Set
Database-Management-System       ER-Model       UGC NET CS 2015 Jun- paper-2
Question 33 Explanation:
A weak entity set do not have any primary key using which we can identify it uniquely. So to uniquely identify a weak entity set it must be associated with its owner entity set and must have total participation in relationship with its owner entity set.

In above figure "Employee" can have many dependents and a dependent can belongs to only one employee. Now two dependents can have same names. So "Dependent" table don't have any primary key to uniquely identify each dependent uniquely. So, it is a weak entity set and "Employee" entity is having "Emp No" as its primary key. Now using "Emp No. along with Name" in "dependent" relation each dependent can be uniquely identify. So we associated "Dependent" set with "Employee" set.
 Question 34
Which of the following statements is FALSE about weak entity set?
 A Weak entities can be deleted automatically when their strong entity is deleted. B Weak entity set avoids the data duplication and consequent possible inconsistencies caused by duplicating the key of the strong entity. C A weak entity set has no primary keys unless attributes of the strong entity set on which it depends are included D Tuples in a weak entity set are not partitioned according to their relationship with tuples in a strong entity set.
Database-Management-System       ER-Model       UGC NET CS 2015 Jun- paper-2
Question 34 Explanation:
A weak entity always have total participation relationship with strong entity. It means that every entry in weak entity set will participate in relationship with strong entity and if a strong entity on which weak entity depends is deleted then total participation condition is exploited. So to avoid this Weak entities are deleted automatically when their strong entity is deleted. So option (A) is correct.
Option (B) is correct. A weak entity is an entity which do not have any primary key to uniquely identify its each entry and this leads to data duplication and data inconsistency in the weak entity. So to avoid this problem the key of a strong entity is duplicated into weak entity to uniquely identify each entry of a weak entity. So option (B) is correct.
Option (C) is also correct. Because until the key attributes of a owner strong entity of a weak entity are not included each entry of weak entity can't be uniquely identified.
Option (D) is false because tuples in a weak entity set are partitioned according to their relationship with tuples in a strong entity set.

In above example the key attribute of "Employee" (which is a strong entity) is partitioning the the tuples of "Dependent" (which is a weak entity) based on the tuples belongs to Emp No. "1" and tuples belongs to Emp No. "2".
So option(D) is false
 Question 35
The E-R model is expressed in terms of :
(i) Entities
(ii) The relationship among entities
(iii) The attributes of the entities
Then
 A (i) and (iii) B (i) and (ii) C (ii) and (iii) D None of the above
Database-Management-System       ER-Model       UGC NET CS 2004 Dec-Paper-2
Question 35 Explanation:
The E-R model is expressed in terms of:
Entities: An entity is a object in Database. An entity is expressed using a rectangular box in an E-R diagram. Example: person, car etc.
Attributes: Nouns which describe nouns. Attributes helps to describe an entity in a better way.
Example: If person is an entity then person name, address, phone number can be its attributes.
Relationship: Any verb which you are going to describe. Example: A person owns a car. Here "owns" is a verb describing relationship between two entities(person and car).

In above diagram Person and Car are two entities
"owns" is defining the relationship between Person and Car.
name, address are the attributes of "Person" entity and number and model are the attributes of "Car" entity.
Note: Excluded for evaluation, Given wrong options.
 Question 36
Specialization is a __________ process.
 A Top - down B Bottom - up C Both (A) and (B) D None of the above
Database-Management-System       ER-Model       UGC NET CS 2004 Dec-Paper-2
Question 36 Explanation:
→ Generalization - the process of defining a general entity type from a collection of specialized entity types.
→ Specialization - the opposite of generalization, since it defines subtypes of the supertype and determines the relationship between the two.
→ Specialization is a top down approach. The following example "Employee" could be a developer or a tester.relationship between the two.
→ Specialization is a top down approach. The following example "Employee" could be a developer or a tester.
 Question 37
The completeness constraint has rules :
 A Supertype, Subtype B Total specialization, Partial specialization C Specialization, Generalization D All of the above
Database-Management-System       ER-Model       UGC NET CS 2004 Dec-Paper-2
Question 37 Explanation:
→ Completeness constraints are both total specialization and partial specialization.
→ The completeness constraints decide whether a supertype instance must also be a membe of at least one subtype.
→ The total specialization rule demands that every entity in the superclass belong to some subclass. Just as with a regular ERD, total specialization is symbolized with a double line connection between entities.
→ The partial specialization rule allows an entity to not belong to any of the subclasses. It is represented with a single line connection.
 Question 38
The entity type on which the __________ type depends is called the identifying owner.
 A Strong entity B Relationship C Weak entity D E - R
Database-Management-System       ER-Model       UGC NET CS 2004 Dec-Paper-2
Question 38 Explanation:
A weak entity of a relation do not have any primary key to uniquely identify it's each tuple. To avoid this problem, the weak entity is associated with the keys of it's identifying owner which is a strong entity.
 Question 39
An Entity - relationship diagram is a tool to represent :
 A Data model B Process model C Event model D Customer model
Database-Management-System       ER-Model       UGC NET CS 2005 june-paper-2
Question 39 Explanation:
A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to properties of the real world entities. For instance, a data model may specify that the data element representing a car be composed of a number of other elements which, in turn, represent the color and size of the car and define its owner. The "data model" may be defined using the entity-relationship data model.
 Question 40
In DBMS, deferred update means :
 A All the updates are done first but the entries are made in the log file later B All the log files entries are made first but the actual updates are done later C Every update is done first followed by a writing on the log file D Changes in the views are deferred till a query asks for a view
Database-Management-System       ER-Model       UGC NET CS 2006 Dec-paper-2
Question 40 Explanation:
→ In deferred update techniques updates are stored to a local storage instead of storing onto the disk. In this technique, a updates is made first later when the transaction gets committed all entries are made in the log file(which is stored into disk) later.
→ If a transaction fails before reaching its commit point, it will not have changed the database in any way so UNDO is not needed. It may be necessary to REDO the effect of the operations that are recorded in the local transaction workspace, because their effect may not yet have been written in the database. Hence, a deferred update is also known as the No-undo/redo algorithm.
 Question 41
What kind of mechanism is to be taken into account for converting a weak entity set into strong entity set in entity-relationship diagram ?
 A Generalization B Aggregation C Specialization D Adding suitable attributes
Database-Management-System       ER-model       UGC NET CS 2014 Dec-Paper-2
Question 41 Explanation:
→ Entity types that do not have key attributes of their own are called weak entity types. In contrast,regular entity types that do have a key attribute are called strong entity types. Entities belonging to a weak entity type are identified by being related to specific entities from another entity type in combination with one of their attribute values. We call this other entity type the identifying or owner entity type, and we call the relationship type that relates a weak entity type to its owner the identifying relationship of the weak entity type.
→ A weak entity type always has a total participation constraint (existence dependency) with respect to its identifying relationship because a weak entity can not be identified without an owner entity.
 Question 42
Relations produced from E-R Model will always be in .
 A 1 NF B 2 NF C 3 NF D 4 NF
Database-Management-System       ER-Model       UGC NET CS 2018 JUNE Paper-2
Question 42 Explanation:
Relations produced from E-R Model will always be in 3NF.
 Question 43
An ER Model includes
I. An ER diagram portraying entity types
II. Attributes for each entity type
III. Relationships among entity types.
IV. Semantic integrity constraints that reflects the business rules about data not captured in the ER diagram.
 A I, II, III & IV B I & IV C I, II & IV D I & III
Database-Management-System       ER-Model       UGC NET CS 2013 Dec-paper-2
Question 43 Explanation:
An ER Model includes
1. An ER diagram portraying entity types.
2. Attributes for each entity type
3. Relationships among entity types.
4. Semantic integrity constraints that reflects the business rules about data not captured in the ER diagram.
 Question 44
Based on the cardinality ratio and participation ________ associated with a relationship type, choose either the Foreign Key Design, the Cross Referencing Design or Mutual Referencing Design.
 A Entity B Constraints C Rules D Keys
Database-Management-System       ER-Model       UGC NET CS 2013 Dec-paper-2
Question 44 Explanation:
Based on the cardinality ratio and participation constraints associated with a relationship type, choose either the Foreign Key Design, the Cross Referencing Design or Mutual Referencing Design.
 Question 45
Data Integrity control uses _______
 A Upper and lower limits on numeric data. B Passwords to prohibit unauthorised access to files. C Data dictionary to keep the data D Data dictionary to find last access of data
Database-Management-System       ER-Model       UGC NET CS 2013 Dec-paper-2
Question 45 Explanation:
→ Any unintended changes to data as the result of a storage, retrieval or processing operation, including malicious intent, unexpected hardware failure, and human error, is failure of data integrity.
→ If the changes are the result of unauthorized access, it may also be a failure of data security.
→ Depending on the data involved this could manifest itself as benign as a single pixel in an image appearing a different color than was originally recorded, to the loss of vacation pictures or a business critical database, to even catastrophic loss of human life in a life critical system.
 Question 46
A Network Schema
 A restricts to one to many relationship B permits many to many relationship C stores Data in a Database D stores Data in a Relation
Database-Management-System       ER-Model       UGC NET CS 2013 June-paper-2
Question 46 Explanation:
→ The network model expands upon the hierarchical structure, allowing many-to-many relationships in a tree-like structure that allows multiple parents. It was most popular before being replaced by the relational model, and is defined by the CODASYL specification.
→ The network model organizes data using two fundamental concepts, called records and sets.
→ Records contain fields (which may be organized hierarchically, as in the programming language COBOL).
→ Sets (not to be confused with mathematical sets) define one-to-many relationships between records: one owner, many members.
→ A record may be an owner in any number of sets, and a member in any number of sets.

 Question 47
In generalisation, the differences between members of an entity is
 A maximized B minimized C both (A) & (B) D None of these
Database-Management-System       ER-Model       UGC NET CS 2010 Dec-Paper-2
Question 47 Explanation:
→ Generalization - the process of defining a general entity type from a collection of specialized entity types.
→ Specialization - the opposite of generalization, since it defines subtypes of the supertype and determines the relationship between the two.
→ Specialization is a top down approach. The following example "Employee" could be a developer or a tester.

 Question 48
An entity instance is a single occurrence of an _______.
 A entity type B relationship type C entity and relationship type D None of these
Database-Management-System       ER-Model       UGC NET CS 2010 June-Paper-2
Question 48 Explanation:
→ Entity type is the heading or schema and entity instance is the value of entity type at a particular instance.
Example:
PERSON(Age, Name, Address) is the Entity Type and PERSON( 28, Anand, Hyderabad) is the entity instance i.e. value of PERSON at a particular instance.
 Question 49
Generalization is _______ process.
 A top-down B bottom up C both (A) & (B) D None of these
Database-Management-System       ER-Model       UGC NET CS 2010 June-Paper-2
Question 49 Explanation:
Generalization can be defined as the process of extracting the common characteristics from two or more classes and combining them into a generalized superclass. Generalization is a Bottom Up approach.

 Question 50
The E-R model is expressed in term of
I. Entities
II. The relationship among entities.
III. The attributes of the entities.
IV. Functional relationship.
 A I, II B I, II, IV C II, II, IV D I, II, III
Database-Management-System       ER-Model       UGC NET CS 2009 Dec-Paper-2
Question 50 Explanation:
The E-R model is expressed in term of Entities, relationship among entities and attributes of the entities.
 Question 51
Specialization is __________ process.
 A top-down B bottom up C both (A) and (B) D none of these
Database-Management-System       ER-Model       UGC NET CS 2009 Dec-Paper-2
Question 51 Explanation:
→ Generalization - the process of defining a general entity type from a collection of specialized entity types.
→ Specialization - the opposite of generalization, since it defines subtypes of the supertype and determines the relationship between the two.
→ Specialization is a top down approach. The following example "Employee" could be a developer or a tester.
 Question 52
An entity has :
(i). a set of properties
(ii). a set of properties and values for all the properties
(iii). a set of properties and the values for some set of properties may non-uniquely identify an entity
(iv). a set of properties and the values for some set of properties may uniquely identify an entity
Which of the above are valid ?
 A (i) only B (ii) only C (iii) only D (iv) only
Database-Management-System       ER-Model       UGC NET CS 2008 Dec-Paper-2
Question 52 Explanation:
An entity has a set of properties and the values for some set of properties may uniquely identify an entity.
 Question 53
Aggregation is :
 A an abstraction through which relationships are treated as lower level entities. B an abstraction through which relationships are treated as higher level entities. C an abstraction through which relationships are not treated at all as entities. D none of the above
Database-Management-System       ER-Model       UGC NET CS 2008 Dec-Paper-2
Question 53 Explanation:
Aggregation: A directional between objects. When an object “has-a” another object, then you have got an aggregation between them, you have got an aggregation between them. Direction between them specified which object contains the other object.
Aggregation is an abstraction through which relationships are treated as higher level entities.

Note: Aggregation is an abstraction through which relationships are treated as higher level entities.
 Question 54
Let E​ 1​ and E​ 2​ be two entities in E-R diagram with simple single valued attributes. R1 and R​ 2​ are two relationships between E​ 1​ and E​ 2​ where R​ 1​ is one - many and R​ 2​ is many - many. R​ 1​ and R​ 2​ do not have any attributes of their own. How many minimum number of tables are required to represent this situation in the Relational Model?
 A 4 B 3 C 2 D 1
Database-Management-System       ER-Model       UGC NET CS 2015 June Paper-3
Question 54 Explanation:
 Question 55

Find minimum number of tables required for converting the following entity relationship diagram into relational database?

 A 2 B 4 C 3 D 5
Database-Management-System       ER-Model       UGC-NET DEC-2019 Part-2
Question 55 Explanation:
There is one to many relationship between R1 and R2. So there will be two tables representing R1 and R2 respectively. And there is a table to represent multivalued attribute B. So total number of tables required to represent given ER diagram is 3.
 Question 56
Which of the following statements is TRUE?
 A The cardinality ratio for a binary relationship specifies the maximum number of relationship instances that an entity can participate in. B The cardinality ratio for a binary relationship specifies the minimum number of relationship instances that an entity can participate in. C The partial participation constraint is also called existence dependency. D The cardinality ratio for a relationship specifies the average number of relationship instances that an entity can participate in.
Database-Management-System       ER-Model       CIL Part - B
Question 56 Explanation:
Cardinality: cardinality ratio for a binary relationship specifies the maximum number of relationship instances that an entity can participate in.
Participation: Participation for a binary relationship specifies the minimum number of relationship instances that an entity can participate in.
 Question 57
Under normal circumstances, the cardinality ratio of the binary relationship “Write” relating “Author” and “Book” entities is:
 A 1 : N B N : 1 C 1 : 1 D M : N
Database-Management-System       ER-Model       CIL Part - B
Question 57 Explanation:
The relationship WRITES shows that one author can write many books and one book can be written by many authors. So the cardinality ratio is M:N
 Question 58
ER modeling technique is a
 A top-down approach B bottom-up approach C left-right approach D none of these
Database-Management-System       ER-Model       TNPSC-2012-Polytechnic-CS
Question 58 Explanation:
1. ER Modeling (Top down Approach)
2. Normalization (Bottom Up approach)
 Question 59
The overall logical structure of a database can be expressed graphically by:
 A Entity relationship model B Relation model C Object based model D Semi structured model
Database-Management-System       ER-Model       TNPSC-2017-Polytechnic-CS
Question 59 Explanation:
The overall logical data structure of a database can be expressed graphically by an E-R diagram. Which consists of rectangle (entity), ellipse (attribute), diamond (relationship), and lines.
There are 59 questions to complete.