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Data Model - PowerPoint PPT Presentation


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Data Model. Different types of data model. Entity – Relationship (E-R) Model. Relational Model Object –Based Data Model Semi structured Data Model Network Model Hierarchical data model. The Entity Relationship Model. ER Model consists of a collection of basic objects called entities

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different types of data model
Different types of data model
  • Entity – Relationship (E-R) Model.
  • Relational Model
  • Object –Based Data Model
  • Semi structured Data Model
  • Network Model
  • Hierarchical data model
the entity relationship model
The Entity Relationship Model
  • ER Model consists of a collection of basic objects called entities
  • Relationships among these objects.
relational model
Relational Model
  • The relational model uses a collection of tables to represent both data and the relationships among those data.
  • It is record based model
  • Each table contains records ( fields or attributes)
relational model cont
Relational Model (cont…)
  • Advantage :
    • Structure independence
    • Conceptual (Theoretical) Simplicity
    • A powerful database management system
  • Disadvantage
    • Transaction Process is not efficient
    • Processing time is low
object based data model
Object –Based Data Model
  • The object oriented model can be seen as extending the E-R model with notions of encapsulation methods (functions) and object identity.
object based data model cont
Object –Based Data Model (cont…)
  • Advantage :
    • Exceptional conceptual simplicity
    • Visual representation
    • Effective communication tool
    • Integrated with the relational database model
  • Disadvantage
    • Limited constraint representation
    • Limited relationship representation
    • No data manipulation language
    • Loss of information content
semi structured data model
Semi structured data model
  • The semi structure data model permits the specification of data where individual data items of the same type have different set of attributes.
  • Example
    • XML ( Extensible Markup Language)
network model
Network Model
  • It is data structure diagram
  • Advantage
    • Data independence
    • Conceptual simplicity
    • Easy to design
  • Disadvantage
    • Lack of structure independence
hierarchical model
Hierarchical Model
  • It uses tree structure diagram
  • Advantage
    • Simple
    • Easy to update
    • Design is simple
    • Database security
    • Efficiency
  • Disadvantage
    • Implementation complexity
    • Difficult to manage
database languages1
Database Languages
  • A database system provides two different types of languages.

They are

  • Data Definition Language
    • To specify the database schema
  • Data Manipulation Language
    • To express database queries and updates
data definition language
Data Definition Language
  • Specifies the databaseschema by a set of definitions
  • Result of compilation of DDL statements is a set of tables that is stored in a special file called data dictionary.
slide14
Data dictionary
    • A data dictionary is a file that contains metadata (that is data about data).
    • This file is consulted before actual data are read or modified in the database system.
  • Active data dictionary
    • Created and maintained automatically by the DBMS
  • Passive Data dictionary
    • Managed by users used more during design and development stage
data dictionary should contain information about
Data dictionary should contain information about
  • Data structures and types of data
  • Domain information about each attribute (columns)
  • Their relation to other entities (Require a user to specify what data are needed from tables)
  • Documentary and technical information regarding systems and design features.
  • Access Control information
  • Details of logic structures that are mapped into the database
  • Resource usage detail
the data values stored in the database must satisfy certain consistency constraints
The data values stored in the database must satisfy certain consistency constraints
  • Domain constraints
    • Example
    • Integer types, character types, date and time types.
  • Referential Integrity
    • Refer another table or attribute
    • Min balance Rs 1000
  • Authorization
    • Permit access (read, insert, update, delete)
data manipulation language dml
Data Manipulation Language (DML)
  • DML is a language that enables users to access or manipulate data as organized by the appropriate data model.
    • Retrieval of information stored in the database.
    • Insertion of new information
    • Deletion of information
    • Modification of information
      • DML
        • Procedural
        • Non procedural (Declarative)
slide18
Procedural DMLs
    • Require a user to specify what data are needed and how to get those data.
  • Non Procedural DMLs
    • Require a user to specify what data are needed without specifying how to get those data.
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