Importance of ER Diagrams

I am a student and I am developing several projects as a part of my academia.

While developing the database for one of the projects, we came across a situation where we thought about whether ERD is necessary or not. Right now, not every one of us are in agreement on developing the ERD first, and then developing database from it.

The majority of people prefers developing the database on the fly verbally according to the system requirementd on paper directly.

Now, I am strict follower of Database principles. I think the database should be developed from the ERD only. So, I just want to know the following:

• Is the industry following these principles?

• Am I just wasting my time on developing an ERD?

• What are the benefits of developing an ERD?

Plain and simple, think of developing a database without an ERD as building a house without a building plan. It might be doable because you think that simply laying a brick one over another is enough to build something, however the moment somebody else takes responsibility over the project there is disaster potential.

In my experience you will not benefit much from ERDs unless you use them in conjunction with CASE tools (ERWin, MySQL Workbench etc.) which will additionally allow you to perform some really helpful operations such as forward and reverse engineering. Even without these functions having a centralized schematic of the complete database is useful because sometimes the constraints implemented in the database itself are not enough to tell the full story about the relationships between particular database entities.

Here is an example involving MySQL which, as you might know, implements several internal storage engines, most notably MyISAM and InnoDB. There are significant differences between them one of the most important one being that MyISAM doesn't support constraints. Despite that fact MyISAM is heavily used for web applications which means that the relational logic needs to be implemented either through business logic (application code) or in another way. The problem is when you forward engineer an ERD with MyISAM tables (entities) MySQL will silently ignore the constraints set by the ERD and you will end up with a database which doesn't clearly identify the nature of the relationships between entities. In other words after you develop the database layout there is no way for the code developers to implement proper business logic without an ERD.

StackExchange Database Administrators Q#9356, answer score: 13