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Database Management Systems notes., Exercises of Database Management Systems (DBMS)

Cochin University of Science and TechnologyDatabase Management Systems (DBMS)

A list of 23 questions and answers related to the ER model and relational database. It covers topics such as entity set, relationship set, attributes, domain, primary key, foreign key, weak entity, strong entity, and ER model. useful for students studying database management systems and related courses.

Typology: Exercises

2019/2020

Available from 10/09/2022

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DBMS
Questions and answers based on SECOND MODULE (first session)
1. ER model uses ---- symbol to represent week entity set
a)
2. Key to represent relationship between 2 tables is called -----
a) Foreign key
3. The person who proposed relational model is---
A) Edgar F. Codd
4. The person having central control over both data and programs accessing that data is called--
a) DBA (Database Administrator)
5. In a relational database a referential integrity constraint can be specified with the help of ---
a) Foreign Key
6. --- are the properties of entities
a) Attributes
7. A ------- is a rule that is used for optimization purposes in a database
a) Constraint
8. The number of entities to which another entity can be associated via a relationship set is
expressed as ---
a) Mapping cardinality
9. A top to bottom relationship among the items in a database is expressed by a ----
a) Hierarchical schema
10. --- express the number of entities to which another entity can be associated via relationship set
a) Mapping cardinality
11. Define Entity Set
a) Entity Set is a collection or a group of 'entities' sharing exactly the 'same set of attributes'.
12. Define relationship set
a) A relationship set is a set of relationships of the same type
13. What is an Attribute?
A) An attribute is an element that takes a value and is associated with an object.eg name,
age
14. Define Domain
a) A domain is a unique set of values permitted for an attribute in a table. For example, a
domain of month-of-year can accept January, February…. December
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DBMS

Questions and answers based on SECOND MODULE (first session)

  1. ER model uses ---- symbol to represent week entity set a)
  2. Key to represent relationship between 2 tables is called ----- a) Foreign key
  3. The person who proposed relational model is--- A) Edgar F. Codd
  4. The person having central control over both data and programs accessing that data is called-- a) DBA (Database Administrator)
  5. In a relational database a referential integrity constraint can be specified with the help of --- a) Foreign Key
  6. --- are the properties of entities a) Attributes
  7. A ------- is a rule that is used for optimization purposes in a database a) Constraint
  8. The number of entities to which another entity can be associated via a relationship set is expressed as --- a) Mapping cardinality
  9. A top to bottom relationship among the items in a database is expressed by a ---- a) Hierarchical schema
  10. --- express the number of entities to which another entity can be associated via relationship set a) Mapping cardinality
  11. Define Entity Set a) Entity Set is a collection or a group of ' entities ' sharing exactly the 'same set of attributes'.
  12. Define relationship set a) A relationship set is a set of relationships of the same type
  13. What is an Attribute? A) An attribute is an element that takes a value and is associated with an object.eg name, age
  14. Define Domain a) A domain is a unique set of values permitted for an attribute in a table. For example, a domain of month-of- year can accept January, February…. D ecember
  1. Define entity a) An Entity is a thing or object in real world that is distinguishable from surrounding environment
  2. Define composite attribute. a) Composite attributes are made of more than one simple attribute
  3. Define derived attribute. a) A derived attribute is an attribute whose value is calculated from other attributes. It need not be physically stored within the database
  1. What is primary key and foreign key a) Primary key uniquely identify a record in the table. Foreign key is a field in the table that is primary key in another table
  1. What is superkey? a) superkey is a set of attributes within a table whose values can be used to uniquely identify a tuple. A candidate key is a minimal set of attributes necessary to identify a tuple; this is also called a minimal superkey
  2. Define relationship a) A relationship, in the context of databases, is a situation that exists between two relational database tables when one table has a foreign key that references the primary key of the other table
  3. Define Week entity and strong entity a) A weak entity is an entity that cannot be uniquely identified by its attributes alone. A strong entity is not dependent of any other entity in the schema. A strong entity will always have a primary key
  4. Compare week and strong entities a) Strong entity is not dependent of any other entity. The strong entity has a primary key. Weak entity is depending on strong entity. A weak entity has the partial key
  5. Define ER model a) Entity Relationship Model (ER Modelling) is a graphical approach to database design. It is a high-level data model that defines data elements and their relationship for a specified software system. An ER model is used to represent real-world objects.

Characteristics of a conceptual data model  Offers Organisation-wide coverage of the business concepts.  This type of Data Models are designed and developed for a business audience.  The conceptual model is developed independently of hardware specifications like data storage capacity, location or software specifications like DBMS vendor and technology. The focus is to represent data as a user will see it in the "real world."

  1. Explain Enhanced Entity Relationship (EER) Model a) Enhanced Entity Relationship (EER) Model is a high-level data model which provides extensions to original Entity Relationship (ER) model. EER Models supports more details design. EER Modelling emerged as a solution for modelling highly complex databases. EER uses UML notation. UML is the acronym for Unified Modelling Language; it is a general-purpose modelling language used when designing object-oriented systems. Entities are represented as class diagrams. Relationships are represented as associations between entities. The diagram shown below illustrates an ER diagram using the UML notation.