a) Neighbour set
b) Strong entity set
c) Owner set
d) Identifying set
Identifying Set
A weak entity set must be associated with an identifying set for it to be meaningful.
Here’s a breakdown:
- Weak Entity Set: An entity set that cannot exist independently and depends on another entity set (strong entity set) for its existence.
- Identifying Set: A set of attributes in a strong entity set that uniquely identifies each entity in the weak entity set.
Essentially, a weak entity set needs a “parent” strong entity set to provide it with a unique identifier. This is because a weak entity set doesn’t have sufficient attributes on its own to form a primary key.
Example:
- Strong Entity Set: Employee (Employee_ID, Employee_Name, Department)
- Weak Entity Set: Dependent (Dependent_Name, Relationship, Employee_ID)