Explain what is weak entity?
1 Answer
  • Entity types that do not have key attributes of their own are called weak entity.

  • Entities belonging to weak entity type are identified by being related to specific strong entities.

  • These strong entities are called identifying entities and relationship with weak entity is called weak relationship.

Weak Entity is represented as:

enter image description here

Weak relationship is represented as:

enter image description here

  • A weak entity has a partial key which is the attribute that can uniquely identify weak entities that are related to another strong entity.

  • For example consider dependent entity, it is a weak entity as it do not have sufficient attributes to from a primary key.

  • It is connected with a strong entity employee.

enter image description here

  • Here the Name attribute is a partial key.

  • Using attributes Name, Age and relation it is not possible to uniquely identify depandant.

  • Thus dependent is weak entity and emp is corresponding identifying strong entity.

Please log in to add an answer.