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Data Model

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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Data Model

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  1. Data Model

  2. 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

  3. The Entity Relationship Model • ER Model consists of a collection of basic objects called entities • Relationships among these objects.

  4. 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)

  5. Relational Model (cont…) • Advantage : • Structure independence • Conceptual (Theoretical) Simplicity • A powerful database management system • Disadvantage • Transaction Process is not efficient • Processing time is low

  6. 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.

  7. 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

  8. 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)

  9. Network Model • It is data structure diagram • Advantage • Data independence • Conceptual simplicity • Easy to design • Disadvantage • Lack of structure independence

  10. Hierarchical Model • It uses tree structure diagram • Advantage • Simple • Easy to update • Design is simple • Database security • Efficiency • Disadvantage • Implementation complexity • Difficult to manage

  11. Database Languages

  12. 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

  13. 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.

  14. 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

  15. 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

  16. 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)

  17. 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)

  18. 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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