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database

  1. 1. WELCOME TO OUR PRESENTATION
  2. 2. CSE-3105 Database Management System Submitted by: Rahij mia ID: CE-19019 Nazmul Haque ID:CE-19005 Samial Mohaimin Efti ID:CE-19009 Md Rubel Hasan ID: CE-19046 Md. Aminul Islam ID: CE-19024 Md. Sakib Hasan ID: CE-18032 Presented to: Md. Mahfuz Reza Associate Professor, Dept. of CSE, MBSTU.
  3. 3. Database Design and the E-R Model
  4. 4. Objective Entity Relationship Model Entity Relationship Diagram(ERD)  Extended Features of ERD
  5. 5. ENTITY RELATIONSHIP MODEL  ER Model- Basic Concepts.  Entity  Attributes and its types  Entity-set and keys  Relationship And Mapping Cardinality
  6. 6. ER Model - Basic Concepts The ER model defines the three most relevant steps. It works around real-world entities and the associations among them. At view level, the ER model is considered a good option for designing databases. • Requirement Analysis • Conceptual Database Design • Logical Database Design
  7. 7. Requirement Analysis The very first step in designing a database application is to understand what data us to be stored in the database, what applications must be built on the top of it, and what operations are we must find out what the users want from the database.
  8. 8. Conceptual Database Design The information gathered in the requirements analysis step is used to develop a high-level description of the data to be stored in database, along with the constraints known to hold over the data. The ER model is one of the high-level or semantic, data models used in database.
  9. 9. Logical Database Design We must choose a DBMS to implement our database design, and convert the conceptual database design into a database schema in the data model of chosen DBMS. Sometimes conceptual schema is called logical schema in Relational Data Model.
  10. 10. Entity An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For example school database, students, teachers, classes, and courses offered can be considered as entities. All these entities have some attributes or properties that give them their identity.
  11. 11. Entity Set An entity set is a collection of similar types of entities. An entity set may contain entities with attribute sharing similar values. For example, a Students set may contain all the students of a school; likewise a Teachers set may contain all the teachers of a school from all faculties. Entity sets need not be disjoint
  12. 12. Attributes Entities are represented by means of their properties, called attributes. All attributes have values. For example, a student entity may have name, class, and age as attributes. There exists a domain or range of values that can be assigned to attributes. For example, a student's name cannot be a numeric value. It has to be alphabetic. A student's age cannot be negative, etc.
  13. 13. Mapping Cardinalities Cardinality defines the number of entities in one entity set, which can be associated with the number of entities of other set via relationship set.
  14. 14. Types of Cardinalities 1.One-to-one One entity from entity set A can be associated with at most one entity of entity set B and vice versa. 2.One-to-many One entity from entity set A can be associated with more than one entities of entity set B however an entity from entity set B, can be associated with at most one entity
  15. 15. Types of Cardinalities (Cont.) 3. Many to One More than one entities from entity set A can be associated with at most one entity of entity set B, however an entity from entity set B can be associated with more than one entity from entity set A. 4. Many to Many One entity from A can be associated with more than one entity from B and vice versa.
  16. 16. ENTITY RELATIONSHIP DIAGRAM Introduction Symbols & Notations Real life example of E-R diagram
  17. 17. Introduction ER-Diagram is a visual representation of data that describes how data is related to each other
  18. 18. SYMBOLS AND NOTATIONS Entities: An entity is an object or concept about which you want to store information. Weak entities: A weak entity is an entity that must defined by a foreign key relationship with another entity as it cannot be uniquely identified by its own attributes alone.
  19. 19. Actions: Actions are represented by diamond shape, and show how two, entities share information in the database. Attribute: This is attribute symbol . Attribute is the unique distinguishing characteristics Of the entity. Multivalued Attribute: A multivalued attribute can have more then one attribute. Derived Attribute: Derived attribute derive from another attribute. SYMBOLS AND NOTATIONS (Cont.)
  20. 20. Real life example of E-R diagram This e-r diagram shows the relation between teacher and student.
  21. 21. EXTENDED FEATURES OF ERD  As the complexity of data increased, it become more and more difficult to use the traditional ER model for database modeling. So some new features are included in the Basic ER model. The combination of Basic ER model and new feature is called Extended ER model. New features are:  Generalization  Specialization  Aggregation
  22. 22.  Generalization is the process of extracting common properties from a set of entities and create a generalized entity from it.  It is a Bottom-up Approach in which two or more entities can be combined to form a higher level entity if they have some attribute in common. Generalization
  23. 23.  Specialization is opposite of Generalization.  In Specialization, an entity is broken down into sub-entities based on their characteristics.  Specialization is a “Top-down Approach” where higher level entity is specialized into two or more lower level entities. Specialization
  24. 24.  Aggregation is used to express a relationship among relationships.  Aggregation is an abstraction through which relationships are treated as higher level entities.  Aggregation is a process when a relationship between to two entities is considered as a single entity and again this single entity has a relationship with another entity. Aggregation
  25. 25. Conclusion So, in this presentation, we studied about Data Models and its parts, i.e Entity Relationship Models, Entity Relationship Diagram and its Extended Features. Beside this, we also learn about the use of them in database system the application, which the information technology field use as one of the major software in computer field.

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