1. Requirements, Collection and Analysis :- During this step, the database designers interview prospective database users to understand and document their data requirements. The result of this step is concisely written as a set of users? requirements. These requirements should be specified as detailed and complete a form as possible. In parallel with specifying the data requirements, it is useful to specify the known functional requirements of the application. These consist of the user?defined operations (or transactions) that will be applied to the database and they include both retrievals and updates. In software design, it is common to use data flow diagrams, sequence diagrams, scenarios, and other techniques for specifying functional requirements.
2. Conceptual Schema :- Once all the requirements have been collected and analyzed, the next steps is to create a conceptual schema for the database, using a high-level conceptual data model. This step is called conceptual design. The conceptual schema is a concise description of the data requirements of the users and includes detailed descriptions of the entity types, relationships, and constraints; these are expressed using the concepts provided by the high-level data model. Because these concepts do not include implementation details, they are usually easier to understand and can be used to communicate with non-technical users. The high-level conceptual schema can also be used as a reference to ensure that all users? data requirements are met and that the requirements do not include conflicts. This approach enables the database designers to concentrate on specifying the properties of the data, without being conceptual with storage details. Consequently, it is easier for them to come up with a good conceptual database design. During or after the conceptual schema design, the basic data model operations can be used to specify the high-level user operations identified during functional analysis. This also serves to confirm that the conceptual schema meets all the identified functional requirements. Modifications to the conceptual schema can be introduced if some functional requirements cannot be specified in the initial schema.
3. Logical Design :- The next step in database design is the actual implementation of the database, using a commercial DBMS. Most current commercial DBMSs use an implementation data model, such as the relational or the object database model, so the conceptual schema is transformed from the high-level data models into the implementation data model. This step is called logical design or data model mapping, and its result is a database schema in the implementation data model of the DBMS.
4. Physical Design :- Finally, the last step is the physical design phase, during which the internal storage structures access paths, and file organizations for the database files are specified. In parallel with these activities, application programs are designed and implemented as datasets transactions, corresponding to the high ? level transaction specifications.