After the introduction to databases and key concepts of what it is and how we can use it – it is time to get down to how we design it. In the past, I have through working in IT heard about database modelling, but never gotten into it properly.
There are several advantages to doing a database model before actually implementing it. As example you can experiment and observe behaviour, as well as improve the model. This will be easier on a model than on a live system. Also, others involved in the project can easily, and without risk of destroying something, get a good overview and communicate any changes or additions to the design. This can often be coworkers or the client itself and its users. This way – we can ensure the program will turn out to be fit for purpose.
So how do I start designing then? There are two different type of documents you will need for a complete model – ERD (Entity Relationship Diagram) and EDF (Entity Description Form).
ERD is the design where you can see how the different entities relate to one another. Personally I use draw.io for making the design, it is a free online service, and you can link it to your Dropbox or download directly. Very user friendly after only playing around with it for a short time.
EDF is a form that lets you enter all the details for every entity (also called table). Here you can set description, attributes, and all other info regarding your database. We were given an example by the school, but I made me a new form in Pages – which made it a lot easier to enter the data and convert into image/PDF.
Combined, these two document types makes out the complete data modelling needed for your database.