Although this isn't used actively in the creation of new FileMaker databases, you certainly may come across it if you open a FileMaker database that has been in use since pre-FileMaker 7 days.
In this example, we have built a relationship that points back to itself, normally called a self relationship. We have created a calculation field that is always equal to 1. Then we used this field as both the parent and child key.
Now, the technique of using a calculation field always equal to one isn’t used that much anymore. For a universal or constant relationship in FileMaker 6, you would have to create a parent and child calculation field that would always equal the same value. In most cases, it would be a calculation field that always equaled 1. If you convert your FileMaker 6 database system to FileMaker 7 and higher, this will still work. FileMaker conversion will not automatically update this relationship to the more elegant comparison operator design. You will need to do that manually.
An example file can be downloaded by clicking (here)
More info about the author and FileMaker in general, contact me at firstname.lastname@example.org.
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