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E-R and Relational Modelling
I have two entities with a 1:M relationship. These entities have a few partial key attributes that are identical.
Is it appropriate for me to create a supertype/subtype model in this context?
Can subtypes have 1:M relationship between them?
In other words...
Common Attribute 1
Common Attribute 2
Subtype1 - entity 1 minus common attributes
Subtype2 - entity 2 minus common attributes
[Subtype1 to Subtype2 has a 1:M relationship]
When creating the Relational Model from this would I do the following...
(1) Copy the key of the parent subtype into the child subtype (as per a one to many relationship)
(2) Copy the key for the supertype entity into each of the subtypes.
In other words....
Common Attribute1 (PK), Common Attribute2 (PK)
Field A (PK), Common Attribute1 (PK), Common Attribute2 (PK)
Field B (PK), Common Attribute1 (PK), Common Attribute2 (PK), Field A (FK)