Handling entity relationship requirements
Entity relationship requirements are sometimes laws, but more often, rules about how pieces of data can relate to one another. An entity is a table, model, or data object. Entity relationships are how these data objects connect to each other. You can see how this happens in an entity relationship diagram, as shown in Figure 14.1:
Figure 14.1 – Entity relationship diagram
This looks a lot like a flowchart and shows not only that the tables are connected, but often the specific variables that connect them, and the markings on the line can denote what kind of relationship these variables have. Again, you will need to look up what the entity relationship requirements are for you, but there are a few main types of requirements:
- Record link restrictions
- Data constraints
- Cardinality
Let’s go ahead and look at these in a little more detail.
Record linkage, or data linkage, is, as...
