Fundamentals of Database Systems questions and answers with explanation for fresher's and experienced for interview, competitive examination and entrance test.

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PART I – Single and Multiple choices:
1) The common types of entities are:
 Strong entities  Weak entities
 Associative entities  All of the above
2) The logical representation of an organization's data is called a(n):
 Database model  Entity-relationship model
 Relationship systems design  Database entity diagram
3) Customers, cars, and parts are examples of:
 Entities  Attributes
 Cardinals  Relationships
4) An entity type whose existence depends on another entity type is called a(n) _____ entity.
 Strong  Weak
 Codependent  Variant
5) A(n) _____ is the relationship between a weak entity type and its owner.
 Member chain  Jump path
 Chain link  identifying relationship
6) A property or characteristic of an entity type that is of interest to the organization is called a(n):
 Attribute  Coexisting entity
 Relationship  Cross-function
7) A person's name, birthday, and social security number are all examples of:
 Attributes  Entities
 Relationships  Descriptors
8) An attribute that can be broken down into smaller parts is called a(n) _____ attribute.  Associative  Simple
 Composite  Complex

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9) The following figure shows an example of:
 A composite attribute  A relational attribute
 A derived attribute  A multivalued attribute
10) An attribute that can be calculated from related attribute values is called a(n) _____ attribute.
 Simple  Composite
 Multivalued  Derived
11) The total quiz points for a student for an entire semester is a(n) _____ attribute.
 Derived  Mixed
 Stored  Addressed
12) Which of the following criteria should be considered when selecting an identifier?
 Choose an identifier that is stable  Choose an identifier that will not be null  Choose an identifier that doesn’t have large composite attributes
 All of the above
13) Which of the following conditions should exist if an associative entity is to be created?
 All the relationships for the participating entities are many-to-many
 The new associative entity has independent meaning
 The new associative entity participates in independent relationships
 All of the above

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14) The number of entity types that participate in a relationship is called the:  Number  identifying characteristic
 Degree  Counter
15) A relationship between the instances of a single entity type is called a(n) _____ relationship.
 Ternary  Primary
 Binary  Unary
Part II - Basic Terms and Data Model:
1) Persons can take the following roles around database systems:
 End users
 DB designers
 DB administrators
 Application Programmers
Decide for each of the following activities, to which role it belongs by writing the respective number in the box. 
Developing the conceptual schema 
Managing user accounts, hardware resources, and backups during the lifetime of the database 
Programming of software that is using the database 
Choice of DBMS 
Analyze requirements for the database 
Programming of a graphical user interface for the database 
Gathering of information about the application field

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2) Classification of Database Management Systems:
a) Name three different data models that can be used in DBMS: Relational Model Object Relational Model Network Model
b) Which data model is used by MySQL? Relational Model
c) Is MySQL a single-user or a multi-user DBMS? Multi-User
Part III – ER to Relational Mapping:
1) Name and explain in brief (just briefly), the steps that are needed to transform an ER diagram into a relational schema.
1. Mapping Strong Entities
2. Mapping Weak Entities
3. Mapping One-to-One relationship
4. Mapping One-to-Many relationship
5. Mapping Many-to-Many relationship
6. Mapping Multi-Valued attributes
7. Mapping N-ary relationship

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Part IV – Challenges:
1) You have the following two figures. Both using the one-to-many relation but in different ways. Are they the same? Yes / No, Give reason.
Using the above "One-to-Many" relationship the implementation is simple and easy; but support one depth and level of relationship, as for instance, a sub-forum can't have other sub-forums!
Using the above recursive relationship it supports both one level and as many level as possible of nested relationships. For instance, a forum can have a sub-forum; the sub-forum still can have other sub-forums and yet that other sub-forums can have sub-forums and so on, so forth.
2) There is something wrong with the following query (The problem is the single quotation-marks with the string). Try to rewrite it with correct syntax using two different methods. SELECT * FROM lecturers WHERE signatory = 'If you tell the truth, you don't have to remember anything';
 SELECT * FROM lecturers WHERE signatory = "If you tell the truth, you don't have to remember anything";
 SELECT * FROM lecturers WHERE signatory = 'If you tell the truth, you don't have to remember anything';
Forum
Sub Forum
has
1
m
Forum
has
1
m
main
sub
Figure 1 - One-to-Man
Figure 2 - Recursive

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آکعی ضَ 02 یک ا جًوي غیر ا تًفاعی تا ذّف تغییر تم یَت آه زَغ پر رٍغ از طریك ارائ آه زَغ کوک ت هتخصصاى عل مَ کاهپی تَر اظت .
اًم ایي ا جًوي ترگرفت از دریای آه پر آب تریي ر دٍ آظیای هیا ک دظت ه جَ آى تیا گًر اظتعذاد اّی فًْت ایي ا جًوي ت دَ ،ُ ایي دریا از
داه اّی ک يْ پاهیر ظرچؽو گرفت ها رٍای ؼوالی ظرزهیي تاظتا یً افغا عًتاى را آتیاری هیک ذٌ ک ایي حالت دریا ذّف ارای خذهات
ا جًوي را ا عًکاض هیذ ذّ.
آکعی ضَ 02 در ظًر دارد تا خذهاتی ها ذًٌ ایجاد فضای ه اٌظة ترای تجلی اظتعذاد اّ ترا گًیختي خلالیت ؼک فَایی علوی هحصلاى دا ػً
پص اٍّى، اًْده ذٌ ظاختي فعالیت اّی ف قَ تر اًه علوی کارتردی، ؼ اٌظایی افراد خلاق، خًث علالو ذٌ ت رْ گیری از هؽارکت آ اًْ در
ارتمای فضای علوی پ تٌَّ ىَ اّ دیگر هراکس آه زَؼی جاهع وّچ ىَ ت لَیذ ا تًؽار ؽًریات علوی تخصصی عل مَ عصری تک اٌل شَی
هعل هَاتی را ت ؼکل ه ثَر آى در جاهع در راظتای رّچ ت تْر ؼذى زهی تذریط، تحمیك پص ػٍّ را اّی رظیذى ت آهال افراد جاهع را فرا نّ هیعازد.
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