Data Modeling - Database Management - Lecture Slides, Slides of Database Management Systems (DBMS)

Data Modeling, Essence of Data Modeling, EntityRelationship, Model Entity, Binary Relationships, OneToOne Binary Relationship, OneToMany Binary Relationship, ManyToMany Binary Relationship, Intersection Data, Cardinality and Modality are some points from this Database Management lecture.

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2011/2012

Uploaded on 12/17/2012

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Data Modeling

Objectives

  • Explain the concept and practical use of data modeling.
  • Recognize which relationships in the business environment are unary, binary, and ternary relationships.
  • Describe one-to-one, one-to-many, and many-to- many unary, binary, and ternary relationships.

Essence of Data Modeling

  • Exploring the different ways that entities can relate to each other as they always do in the real world
  • Devising a way of recording, of diagramming, the entities and the ways in which they interrelate in the business environment

Entity-Relationship (E-R) Model

  • A diagramming technique
  • Diagrams entities (with attributes) and the relationship between the entities.
  • There are many variations of E-R diagrams in use.

E-R Model Entity (and its attributes)

  • Entity type’s attributes are shown below the separator line.
  • An asterisk denotes attribute(s) that constitute the entity type’s unique identifier.

Relationships

  • Associations between entities
  • Different kinds:
    • Binary relationships
    • Unary relationships
    • Ternary relationships

Cardinality

  • Represents the maximum number of entities that can be involved in a particular relationship. - One-to-One Binary Relationship - One-to-Many Binary Relationship - Many-to-Many Binary Relationship

One-to-One Binary Relationship

  • A single occurrence of one entity type can be associated with a single occurrence of the other entity type and vice versa.

Many-to-Many Binary Relationship

• M-M

  • “many” can be either an exact number or have a known maximum.

Cardinality

Cardinality & Modality

Intersection Data

  • Describes the relationship between two entities.
  • Used with many-to-many relationships.
  • Represented on E-R diagram in a special five-sided intersection data box, which is attached to the relationship diamond between the two entity boxes.

Associative Entity

  • Entities can have attributes; many-to-many relationships can have attributes.
  • Many-to-many relationship may be treated similarly to entities in an E-R diagram.

Associative Entity

  • Should you diagram as associative entity or many-to-many relationship? - personal taste - follow company standards
  • The unique identifier of the associative entity is usually the combination of the unique identifiers of the two entities in the many-to- many relationship.