Advanced Relationship Techniques - FileMaker Pro 13: The Missing Manual - page 720

because the Jobs TO is only one table occurrence away from the Invoices TO. But, remem-
ber, you can also have FileMaker stand on the Invoices TO and get the Customer's name and
address data, which is two TOs away. And to the degree that you have an unbroken line of
TOs, it's possible to get data from many more “hops” away from the current context. In the
sample database, you could “stand” on the Payments TO and get data from the Customer TO,
four hops away. And since most relationships are bidirectional ( Reviewing Relationship
Concepts ) , you could also stand on the Customer TO and view data from the Payments table
or any point in between.
Some other databases make you jump through flaming hoops to get to data that's far away
from your current context. But FileMaker takes its “ease of use” label seriously, so it handles
the complexity for you. In exchange though, you can't create ambiguous (or circular) rela-
tionships. For example, you can't create another relationship between the Expenses and Pay-
ments TOs because they are already related to one another through Jobs and Invoices and In-
voice payments. So in any Relationships Graph, there is always one, and only one, unam-
biguous path between any two TOs. Now that you see what ambiguity means, it's time to
learn how FileMaker prevents you from creating it in your graph.
1. Choose File → Manage Database and then click the Relationships tab .
The Relationships graph appears.
2. Drag the Invoices_currentJob::JobID field to the Jobs::JobID field .
The Add Relationship dialog box appears, along with a warning that you are trying to
make a relationship that won't be allowed. See Figure 14-2 .
3. Click OK to create the TO .
A TO with the name “Jobs 2” appears on the graph. Its source table is Jobs. FileMaker
makes a guess about which table you need an occurrence for, based on where you
dragged. You can learn more about how this works in the box on the facing page. This
behavior is so reliable that some people intentionally drag to an ambiguous spot on
the graph because it's quicker than clicking the Add Relationship button and then set-
ting up the relationship.
4. If you don't like FileMaker's guess, click Cancel .