Common problems in data models
Creating a correct data model is only the beginning of providing a good data platform, as users of these data models must also be aware of problems that can arise because of the nature of operations on relational models.
In the following section, we present the most common problems you will encounter.
Fan trap
The fan trap is a very common problem that can happen every time you have a join in a one-to-many relationship. It is not a problem of the relationship, but of how you might use it.
The fan trap problem causes the calculations done on measures joined from the one side of the one-to-many relationship to be wrong.
This is only a problem if you use a measure that is on the one side of a one-to-many relationship, when grouping/working at the granularity of the entities on the many side. This happens because the join will duplicate the measures to match the cardinality of the many side.
Let’s look at a simple example based on...
