Relationships

In situations where the two entities in the model have one or more relationships, like in our example here:

You need to map the relationships as well. The way to think about this is what in the data is driving the relationship. In the case here, we see that it's in fact the ORDER_ITEM entity that is driving the relationship to the ORDER and PRODUCT entities.

Just like for attributes, you need to select the source table for the data and either select a column in the source data or write your custom Source Expression.