From Dwayne Wright PMP
Certified FileMaker Developer
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In data modeling, Crows Feet is a common term for a graphical representation that a relationship between two entities may have multiple matching records. Data modeling refers to a mapping of relationships, most commonly done in an Entity Relationship Diagram (ERD). If you want a more in depth description about the historical account of crows feet relationship display, do a search in wikipedia for Entity-relationship model.
In the FileMaker relationship graph, Crows Feet is a common term for a graphical representation that a relationship between two table occurrences may have multiple matching records. In FileMaker, a crows foot helps indicate that there is a one to many or a many to many relationship.
In the FileMaker relationship graph, you will see crows feet automatically show up or not. It is not something you can change but FileMaker is pretty intuitive about its assignment of a crows foot. By process of elimination, FileMaker will assign a crows foot to every relationship unless it sees a good reason not to. I haven’t come across a definitive list of what good reasons FileMaker is using but I can submit my observations.
In the database I use to create, store and organize my blogs, I have a central table called Blog Stuff. In my relationship graph, I use an Anchor / Buoy method. So no two main tables touch and my Blog Stuff table occurrence is linked to 15 other table occurrences. Out of those 15, only one of them does not have a crows foot representation.
The one relationship, sans the crows foot, is the advertisement record I link to each blog posting. So in my Blog Stuff table, I have a foreign key that contains the serial number of the advertisement I am using. FileMaker detects this and does not assign a crows foot.
A crows foot can appear on either end of a relationship. If a field is a serial number, it will not have the crows foot on that end but it can have a crows foot on the other end. This indicates that there are many possible related records possible going in that direction.
Now if both match fields in the relationship are set to have unique values only, that would be a clear indication to FileMaker that this is a one to one relationship.
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© 2008 - Dwayne Wright - dwaynewright.com
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