Foreign Key Propagation
A row of data in a table is the fundamental relationship in a Relational Database. Connecting two or more tables through their Primary Keys (PK) and Foreign Keys (FK) is the fundamental way to extend a relationship across multiple tables (and implicitly joining the rows of the tables).
From this point forward,on this page , relationship refers to the connection between two tables. Relationships are visible on the diagram as lines, with adorned pivoting end points. The end points pivot so the adornment, which is part of a visual representation of the relationship between the tables, can attach to the entity at a right angle.
ER-Designer supports four types of relationships. They are: Identifying, non-identifying mandatory, non-identifying optional, and non-specific. We will cover these relationship types in the help and tutorial sections. For now, we are going to focus on the FK propagation support in ER-Designer.
The screen shot at the right shows an identifying relationship (Entity_1.ID to Entity_3's primary key as foreign key Entity_1_ID). It shows an non-identifying mandatory relationship (Entity_2.ID to Entity_3.Entity_2.ID). Notice how the Identifying relationship propagates the FK into the PK of the child entity. And how the Non-identifying relationship propagates the PK to the non-primary-key area in Entity_3.