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 Disadvantage
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 database schema 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. Active 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. Referential Integrity
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 Non 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.