DATA MODELING AND ENTITY RELATIONSHIP DIAGRAM:-
Data modelings the process of designing logical structure of a database with a diagram using text and symbols to represent the way data needs to flow. This diagram is called Entity Relationship diagram EFC Data models define how data is connected to each other and how they are processed and stored inside the system. Data models are built during the analysis and design phases of a protect to ensure that the requirements for a new application are fully understood. A data mode can be thought of as a diagram or flowchart that illustrates the relationships between data Well-documented conceptual, logical and physical data models allow stake-holders to identify errors and make changes before any programming Code has been written.
Data model designers often use multiple models to view the same data and ensure that all processes, entities relationships and data flows have been identified. There are several different approaches to data modeling, including: Conceptual Data Modeling-identifies the highest-level relationships between different entities. Enterprise Data Modeling – similar to conceptual data modeling, but addresses the unique requirements of a specific business.
Logical Data Modeling – illustrates the specific entities, attributes and relationships involved in a business function. Serves as the basis for the Creation of the physical data model.
Physical Data Modeling – represents an application and database-specific implementation of a logical data model. When a system developer designs a new database system, one Crucial task is to identify and state the data needs of the organization. This describes how the data elements in the system are to be grouped. The following terms are used in building a picture of the data requirements.
Entity: An entity is a thing of interest to an organization about which data is to be held. Examples of entities include Student, Customer, Employee, Stock Item, Supplier, etc.
Attribute: An attribute is a property or characteristic of an entity. Examples of attributes associated with a Customer include Customer ID, Surname, initials, Title, Address, etc.
Relationship: A relationship is a link or association between entities. An example is the link between Dentist and Patient; one dentist has many patients, but each patient has only one dentist.
Keys: It is an attribute used to identify a record in a database. Keys are used to create links – between tables to avoid duplication of data in various tables.