We have now looked at the background of data modelling and where it all began. Clay tablets, lists, books and now databases. But behind all of these is the need to model the data in a way that makes it easy to use. In this way, data modelling is both a simple and complex area [...]
We have reviewed data modelling connection types over the past several weeks (see Connections) and seen that a few simple names can describe different types of connections in a general way: One-to-one (mandatory or optional). One-to-many (see One-to-many-relationships). Many-to-one. Many-to-many (see Many-to-many relationships). […]
A many-to-many relationship is also best shown by example. One author can write many books – this is a one-to-many relationship. However, one book can also have many authors. Putting these two facts together, we see a many-to-many relationship. Two “one-to-many” relationships in opposite directions. Since this is not always easy to understand, let’s look [...]
As we saw in the list of relationships at the end of last week’s newsletter, most relations do not demand one and only one connected object. It is much more common for the limit of one object to be only on one end of the connection. […]
Optional one-to-one relationships Optional one-to-one relationship are more common than mandatory one-to-one relationships, both in life and in data modelling. Sometimes an object may be optionally connected to at least one other object. One example is a car, which may be registered or licensed for use on the road or it may be allowed to [...]
Types of connections Connections are the most important and difficult things in modelling. Objects only rarely exist with no connections to other objects. The saying “No man is an island”[1] expresses this with regard to people, and other objects are just the same. […]
In this article we continue our simple data modelling example. We have named our database table, and now we need columns to store the information about each pot. Naming columns is another minefield, just like naming tables. All sorts of logic can be applied to avoid naming conflicts and ensure consistency. We will ignore this [...]
Simple Data Modelling Everyone has to start somewhere. An expert in any field does their first work sometime. Every data modeller does their first piece of simple data modelling at some time. Whether you are an expert or someone wanting to start newly with data modelling, here is an example of data modelling in its [...]
Using a Database The last post looked at what we should model, and the importance of scale and magnitude. Now we need to acknowledge that the data we model will normally be stored in a database. Modelling is the mapping between the real world and the filtered picture of the real world that we wish [...]
Surrounded by things All around us are physical things: chairs, tables, computers, walls, doors, people, cars, houses, trees, roads and many other things. How we think about each depends on our point of view. Walls, floors, ceilings, doors and windows make rooms, and houses are made up of rooms. A builder needs to know all [...]