Ppt of dbms e r features

This ppt will be usefull to all the engineering student of 3rd sem.

1. GANDHINAGAR INSTITUTE OF TECHNOLGY Department of Information Technology E-R Features Group ID: IT_A1_10 Students Names: Akabari Nirali ( 130120116002) Akanksha Sharma (130120116003) Guided By: Prof. Anirudhdha Nayak Database Management System(2130703)

2. Presentation outlines: E-R concept Specialization Generalization Aggregation E-R diagram notation for representing specialization E-R diagram with redundant relationship E-R diagram with Aggregation

3. Basic E-R concepts The original concept of the entity-relationship model was given by Chen in 1976. High level conceptual(logical) data model. Widely used in database design to represent a conceptual schema. A conceptual schema represented by the E-R model is called an E-R schema.

4. The basic notation used in E-R diagram are illustrated below: An entity set An Attribute A Relationship set Link between an entity set & attribute

5. Specialization Specialization is the process of defining sub-class based on some distinguishing characteristics. In other words, specialization identifies the sub-sets possesses some attributes Specialization is a top-down process to define super-class/sub-class relationships.

6. Generalization Generalization is the process of defining a super-class from sub-classes based on some common characteristics. In other words, generalization identifies a super-class from different entity-sets(or sub-classes). Generalization is a bottom-up process to define super-class/sub-class relation.

7. A bottom-up design process – combine a number of entity sets that share the same features into a higher-level entity set. Specialization and generalization are simple inversions of each other; they are represented in an E-R diagram in the same way. The terms specialization and generalization are used interchangeably.

8. Aggregation Aggregation is an abstraction through which relationships are treated as higher level entities. Thus, for our example, we regard the relationship set works on as a higher-level entity set called works on. Such an entity set is treated in the same manner as is any other entity set. Figure shows a notation for aggregation commonly used to represent this situation.

9. E-R Diagram With Aggregation

10. E-R Diagram With Redundant Relationships