Strong and Weak Entity Sets
Strong Entity Sets
The entity types containing a key attribute are called strong entity types or regular entity types.
eg:- The Student entity has a key attribute RollNo which uniquely identifies it, hence is a strong entity.
Weak Entity Sets
An entity set may not have sufficient attributes to form a primary key. Entity types that do not contain any key attributes, and hence can not be identified independently are called weak entity sets.
A weak entity can be identified uniquely only by considering some of its attributes in conjunction with the primary key attribute of another entity, which is called the Identifying Owner entity.
The entity types containing a key attribute are called strong entity types or regular entity types.
eg:- The Student entity has a key attribute RollNo which uniquely identifies it, hence is a strong entity.
Weak Entity Sets
An entity set may not have sufficient attributes to form a primary key. Entity types that do not contain any key attributes, and hence can not be identified independently are called weak entity sets.
A weak entity can be identified uniquely only by considering some of its attributes in conjunction with the primary key attribute of another entity, which is called the Identifying Owner entity.