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Autor: anton • September 30, 2010 • 866 Words (4 Pages) • 915 Views
Database Systems has a practical, hands-on approach that makes it uniquely suited to providing a strong foundation in good database design practice. Database design is more art than science. While it's true that a properly designed database should follow the normal forms and the relational model, you still have to come up with a design that reflects the business you are trying to model. This paper shows describes design process of database project.
The importance of Completing the Design Process
An important point to keep in mind is that the level of structural integrity and data integrity is in direct proportion to how thoroughly the design process is followed. The less time spent on the design process, the greater the risk of encountering problems with the database. While thoroughly following the database design process may not eliminate all of the problems you may encounter when designing a database, it will greatly help to minimize them. Also in an RDBMS software program a well-designed database is easier to implement than a poorly designed database. (Michael J. Hernandez, 1996)
Key database Design Concepts
Before a design effort can proceed full speed ahead, the designer must first take time to understand the business. Understanding the business involves understanding the entities, data, and rules within an organization, and then converting these attributes of the business into a business model. Then, the designer must have a solid comprehension of the proposed database model. Finally, the designer will convert the business model into a database model, using a design methodology, whether automated or a manual process.
(Ryan Stephens & Ronald Plew, 2002)
General Design Process
Following table list general steps of database design
1 Requirements collection and analysis
2 Conceptual database design
3 Choice of a DBMS
4 Data model mapping (also called logical database design)
5 Physical database design
6 Database system implementation
(Elmasri, Ramez, & Navathe, Shamkant B., 1994)
Creating the application is the last stepÐŽÐ„not the first! Many developers take an idea for an application, build it, then go back and try to make a set of database tables fit into it. This approach is completely backwards, inefficient, and will cost a lot of time and money.
Before starting any application design process, sit down and talk it out. If you can't describe your applicationÐŽÐ„including the objectives, audience, and target marketÐŽÐ„then you're not ready to build it, let alone model the database.
Once you can describe the actions and nuances of your application to other people and have it make sense to them, you can start thinking about the tables you want to create. Start with big flat tables because, once you write them down, your newfound normalization skills will take over. You will be able to find your redundancies and visualize your relationships.
The next step is to do the normalization. Go from flat table, to first normal form, and so on, up to the third normal form if possible. Use paper, pencils, Post-it Notes, or whatever helps you to visualize the tables and relationships. There's no shame in data modeling on Post-it Notes until you're ready to create the tables themselves. Plus, they're a lot cheaper than buying