What are the benefits or disadvantages of ER diagrams? Why bother with a logical design and not just create tables and columns (physical design) directly?
Entity-relationship diagrams (ERDs) are a logical representation of data that describes the relationships among entities and attributes. The central reasons for choosing an entity relation (ER) model over physical design are as follows (Al-Shamailh, 2015):
- Conceptual simplicity. If relationships between entities and attributes are known, an ERD can be quickly drawn.
- Explicit visual representation. The database structure can be easily comprehended after consulting the diagram.
- Communication effectiveness. Standard symbols representing different information facilitate understanding of the working of the database after completion.
- Immense flexibility. ER data model can be easily converted into any other data model with minor manipulations.
The characteristics mentioned above are also the primary benefits of ERDs. However, it is necessary to state the disadvantages of the concept to acquire a holistic picture of the matter:
- Limited relationship representation. The model is limited in relationships as compared to other data models.
- No representation of data manipulation. The ways of showing data manipulation in ERD are comparatively intricate making the model find only limited use.
- No industry standard for notation. The notation standards vary depending on the choice of a developer generating confusion while reading the diagrams.
Al-Shamailh, A. (2015). An experimental comparison of ER and UML class diagrams. International Journal of Hybrid Information Technology, 8(2), 279-288. Web.