Database Management System · Unit 2
Entity-Relationship Model
Exam-focused notes for Entity-Relationship Model (Database Management System, BIT202): what the TU syllabus asks and how it has actually been tested, with 7 solved past questions from this unit.
What this unit covers
- ER diagram purpose and symbols
- Entities and attributes
- Attribute types and derived attributes
- Relationships and cardinality
- Weak entities and partial keys
- Generalization and specialization
- Extended ER model constraints
ER diagram purpose and symbols
What is the need for an ER diagram? Design an ER diagram that contains at least five entities. One of the entities must be a weak entity. There should be many to many relationships between the two strong entities. One of the entities should have derived and multi-valued attributes. Any one strong entity should have total participation in a relationship with another entity. Use your own assumptions as per required.[10]
--- An Entity-Relationship (ER) Diagram is a high-level conceptual data model that graphically represents the structure of a database. The need for an ER diagram arises due to the following reasons: 1. Visual Representation of Data: It provides a clear, pic...
Full solved answer →Explain the various Symbols used in E-R Model?[10]
The Entity-Relationship (E-R) Model is a high-level conceptual data model used to describe the structure of a database. It was proposed by Peter Chen in 1976. The E-R model uses a set of standard graphical symbols to represent data and the relationships amo...
Full solved answer →What is an E-R Diagram? Explain various symbols used in the E-R Diagram.[5]
An Entity-Relationship (E-R) Diagram is a graphical/pictorial representation of the logical structure of a database. It shows the entities (objects) in a system, the attributes of those entities, and the relationships between them. It was introduced by Pete...
Full solved answer →Extended ER model constraints
Discuss the various types of constraints used on Extended ER Model. [5]
The Extended Entity-Relationship (EER) model adds additional semantic concepts to the basic ER model. Among the most important additions are constraints on specialization and generalization, which control how entities participate in subclass/superclass rela...
Full solved answer →Attribute types and derived attributes
What is Attributes? Explain different types of Attributes with example. [5]
An attribute is a property or characteristic that describes an entity in an Entity-Relationship (ER) model. Attributes represent the data stored about an entity and are depicted as ovals in an ER diagram. Example: For an entity STUDENT, attributes can be Ro...
Full solved answer →Weak entities and partial keys
What do you mean by weak entity and partial key?Design an ER diagram for following scenario; In film industry, producers produce movies. Producers have their name, age and budget as attributes. They are uniquely identified by prod_id. All the movies have their title, year, and release date. No movies can have same title. Every movies must be played by actor. An actor can play many movies. Actors have Fname and Lname to uniquely identify them. The actors have charge_rate as well. A single movie can have many producers and a producer can produce many movies.[3+7]
--- (a) Weak Entity and Partial Key A weak entity is an entity type that does not have a key attribute of its own. It cannot be uniquely identified by its own attributes alone. A weak entity depends on another entity (called the identifying entity or owner ...
Full solved answer →Generalization and specialization
What do you mean by generalization specialization in EER? Illustrate with examples. [5]
The EER model extends the basic ER model with additional concepts to represent more complex real-world situations. Generalization and Specialization are two complementary processes used to organize entities into hierarchies. --- Specialization is a top-down...
Full solved answer →Make Unit 2 stick
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