Database Design Process
The first step of database design is requirement collection and analysis. During this step, the DB designers interview prospective info users to grasp and document their information necessities. The results of this step may be a brief written set of user’s needs.
Once all the necessities are collected and analyzed consecutive step two is to make an abstract schema for the database, employing a high-level abstract data model. This step is called conceptual design which consists primarily of defining the data elements to be included in the database, the relationships that exist between them, and the value constraints that apply.
The abstract schema may be a pithy description of the information necessities of the users and includes elaborated descriptions of the entity sorts, relationships, and constraints. These area units expressed exploitation of the ideas provided by the high-level data model. Because these concepts do not include implementation details, they are usually easier to understand and used to communicate with nontechnical users. The high-level conceptual schema can also be used as a reference to ensure that all user’s data requirements are met and that the requirements do not include conflicts. This approach enables the database designers to concentrate on specifying the data, without being concerned with storage details.
The next step in DB design is that the actual implementation of the database, employing an industrial database management system (DBMS). Most current industrial DBMSs use in the implementation of data models. like the relative or object data model. that the abstract schema is remodeled from the high-level data model into the implementation data model. We can introduce this step as a logical creation or data model mapping. The ER diagram is converted into set relations/tables in the relational data model. Here, to represent the data, logical structures are defined. The outcome of logical database design is a set of well-structured relations that has a logical relationship among them.
Finally, the last step is that the physical style section, throughout that the interior storage structures, access ways, and file organizations for the database files area unit specific. In parallel with these activities, the application programs area unit designed and enforced as data group actions akin to the high-level transaction specifications. Physical data-style determines the body of the information and includes such selections on what access methodology is accustomed to retrieve knowledge, and what indexes are engineered to enhance the performance of the system.
Database design decisions are documented in the data dictionary. The DBA controls the contents of the data dictionary and records there as metadata the names of data elements, files, screens, reports forms, and life. The manipulation is very carefully controlled by the DBA since the data in the data dictionary are vital to the proper functioning of the database system as a whole.
ER Concepts and Terminology
An entity-relationship model is a detailed conceptual representation of the data for an organization or for a business area.
The ER model is expressed in terms of entities within the business environment, the relationships among those entities, and therefore the attributes (properties) of both entities and their relationships.
An ER model is a graphical representation, and an ER format is usually expressed as an ER diagram.