What is the type of relationship between weak and strong entity?
The relationship between a weak entity type and strong entity type is called an ‘identifying relationship’ and shown with a double outlined diamond instead of a single outlined diamond. The strong entity is some times called the dominant entity and the dependant entity is called a subordinate entity.
What is the relationship between a weak entity and a strong entity give examples?
The relationship of two strong entities is represented by a single diamond….Difference between Strong and Weak Entity:
|S.NO||Strong Entity||Weak Entity|
|1.||Strong entity always has a primary key.||While a weak entity has a partial discriminator key.|
|5.||Strong entities have either total participation or not.||While weak entity always has total participation.|
Can weak entity have relationship?
‘Can a weak entity be related to another weak entity’ I would say No. A weak entity has no primary key of its own but does have a foreign key which is linked to the PK of another entity. Thus if you have two weak entities with the same FK id they are infact related to the same strong entity rather than each other.
What is weak relationship in DBMS?
A weak, or non-identifying, relationship exists if the primary key of the related entity does not contain a primary key component of the parent entity. Company database examples include: Customer(CustID, CustName)
What is a strong relationship in ERD?
Strong (Identifying) Relationship. Child entity is existence-dependent on parent. PK of Child Entity contains PK component of Parent Entity. Usually occurs utilizing a composite key for primary key, which means one of this composite key components must be the primary key of the parent entity.
What are the 3 main components of entity relationship diagram?
ER diagrams or ERD’s are composed of three main elements: entities, attributes, and relationships.
What is weak relationship in ER diagram?
A weak or non-identifying relationship exists between two entities when the primary key of one of the related entities does not contain a primary key component of the other related entities. A strong or identifying relationship is when the primary key of the related entity contains the primary key of the “parent”.
Is the relationship between a weak entity type and its owner?
A single occurrence of an entity is called an entity instance. The relationship between a weak entity type and its owner is an identifying relationship. An entity type on which a strong entity is dependent is called a covariant entity. An entity type name should always be a singular noun.
What is strong relationship in database?
A strong or identifying relationship is when the primary key of the related entity contains the primary key of the “parent”.
What is strong relationship and weak relationship?
A strong relation arises between types of entities in cases where the existence of one type of entity is impossible without another type of entity. A weak relation arises between two types of entities in the case when there is no direct relationship between them.
What is weak entity and weak relationship?
Weak entity is dependent on strong entity and cannot exists without a corresponding strong. It has a foreign key which relates it to a strong entity. A weak entity is represented by double rectangle. Relationship between a strong entity and a weak entity is represented by double diamond.
What is weak entity in ER diagram?
A weak entity is a type of entity which doesn’t have its key attribute. It can be identified uniquely by considering the primary key of another entity. For that, weak entity sets need to have participation. In above ER Diagram examples, “Trans No” is a discriminator within a group of transactions in an ATM.
What is the difference between weak entity and strong entity?
A weak entity is an entity set that cannot be uniquely identified by its attributes alone.
What is strong entities vs weak entities?
Strong entity always has a primary key
What is an example of a weak entity?
Example for weak entity In the ER diagram, we have two entities building and apartment; Building is a strong entity because it has a primary key attribute called building number which is capable of uniquely identifying all the flats present in the apartment ; Unlike building, apartment is weak entity because it does not have any primary key and door number here acts only as a discriminator
Can weak entity be converted into strong entity?
i. Though weak entity set can be converted into strong entity set by simply adding appropriate attributes, this approach results in the redundant storage of primary key. ii. The primary key of a weak entity set can be inferred from its relationship with the strong entity set.