What are strong and weak entities?
What are strong and weak entities?
A strong entity is not dependent on any other entity in the schema. Various strong entities, when combined together, create a strong entity set. Weak Entity: A weak entity is dependent on a strong entity to ensure its existence. Unlike a strong entity, a weak entity does not have any primary key.
What is weak entity set and strong entity set?
Differences between Strong entity set and Weak entity set-
| Strong entity set | Weak entity set |
|---|---|
| It contains sufficient attributes to form its primary key. | It does not contain sufficient attributes to form its primary key. |
What is weak and strong entity sets explain with example?
Weak entities are dependent on strong entity. Its existence is not dependent on any other entity. Strong Entity is represented by a single rectangle − Continuing our previous example, Professor is a strong entity here, and the primary key is Professor_ID.
What is weak entity set give an example?
A weak entity is one that can only exist when owned by another one. For example: a ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a strong entity because it also can exist without being attached to a CAR. Just to play with it, question is strong entity type and answer is weak.
How are strong and weak entity sets classified?
The entity can be classified into two basic categories, strong entity set and weak entity set. An entity set that has a primary key is the strong entity set. An entity that doesn’t have a primary key is a weak entity set. A weak entity set is dependent on one strong entity set to distinguish its entities.
How is a strong entity complete by itself?
A strong entity is complete by itself and is not dependent on any other entity type. It possess a primary key which describes each instance in the strong entity set uniquely. That means any element in the strong entity set can be uniquely identified.
Which is the primary key of a strong entity?
It is denoted by a single rectangle. A strong entity always has the primary key in the set of attributes that describes the strong entity. It indicates that each entity in a strong entity set can be uniquely identified. Set of similar types of strong entities together forms the Strong Entity Set.
What are weak and strong entities in DBMS?
In this article, we will learn about Weak Entity and Strong Entity in DBMS. The entity defines the type of data stored, simply it is nothing but a database table . We have the following two types of entities based on Unique Identification – The strong entity is represented by a single rectangle .