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A table's unique identifier is its primary key, and where it occurs in another table, it is a foreign key.
A relationship line has a one termination at the primary key and many terminations at the foreign key representing the 1 and many ends of the relationship.
To open relationship properties, in an ERD click on the relationship line. Relationships are not listed in the repository. It would help to repeat here that the crow's foot line ending indicates the many end of a one-to-many or many-to-one.
Most of the properties of a relationship are automatically set by the ERD, so are read-only. You can add details to the description.
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