Can a weak entity be dependent on another weak entity?

Can a weak entity be dependent on another weak entity?

‘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 a weak entity give another example of a weak entity?

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 would you map weak entities of weak entities?

2. Mapping of Weak Entity Types. For each weak entity, create a table that includes all of it’s simple attributes. And include a foreign key points to the primary key of the owner entity, where the foreign key and partial key will be the primary key of the weak entity.

What is the difference between weak entity and strong entity?

Strong entity always has a primary key. While a weak entity has a partial discriminator key. Strong entity is not dependent on any other entity. Weak entity depends on strong entity.

What is the participation of a weak entity in a relationship?

A weak entity always has a total participation constraint with respect to its identifying relationship because it cannot be identified independently of its owner identity. A weak entity may have a partial key, which is a list of attributes that identify weak entities related to the same owner entity.

Can a weak entity be used as an independent entity?

A weak entity cannot be used independently as it is dependent on a strong entity type known as its owner entity. Also, the relationship that connects the weak entity to its owner identity is called the identifying relationship.

How is a weak entity represented in ER?

Like strong entity, weak entity does not have any primary key, It has partial discriminator key. Weak entity is represented by double rectangle. The relation between one strong and one weak entity is represented by double diamond.

When should we use weak entities when modelling a database?

If, after you have done this, you look at a particular entity and it has the characteristics of a “weak” entity, you can document or diagram it accordingly, if for some reason you feel the need to explicitly call this out or for the sake of formality.

How are partial keys used to identify weak entities?

Partial Keys are set of attributes with the help of which the tuples of the weak entities can be distinguished and identified. Note – Weak entity always has total participation but Strong entity may not have total participation.