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Weak entity means an entity which doesnt uniquely exist and requires another foreign entity for its complete representation.
For example, we have a University database and we have a table of departments having dept_id as its primary key. Now, a department cannot exist independently unless there is a university, so this entity needs university id as well to represent it.
What else can I help you with?
Which entity type depends is called identifying owner?
weak entity
Can an identifying relationship of a weak entity type will be of a degree greater than two give example?
Sure thing, honey. An identifying relationship of a weak entity type can definitely have a degree greater than two. For example, let's say we have a weak entity type called "Order Item" that depends on both "Order" and "Product" entities to uniquely identify it. In this case, the identifying relationship would have a degree of two (connecting "Order" and "Product") but the weak entity type itself would have a degree of three. Hope that clears things up for ya!
Why do we need weak entity sets?
why do we need weak entity in database when we can make it strong entity?
Can weak entity be converted into strong entity in DBMS?
A weak entity set can always be make into strong entity set by adding to its attribute of its identifying entity set. For a weak entity set, we add columns to the table corresponding to the primary key of the strong entity set on which the weak set is dependent.
Explain the difference between a weak and a strong entity set?
An entity set that does not possess sufficient attributes to form a primary key is called a weak entity set. One that does have a primary key is called a strong entity set. The discriminator (or partial key) of a weak entity set is the set of attributes that distinguishes among all the entities of a weak entity set The existence of a weak entity set depends on the existence of a identifying entity set. It must relate to the identifying entity set via a total, one-to-many relationship set from the identifying to the weak entity set We depict a weak entity set by double rectangles in E-R diagram. We underline the discriminator of a weak entity set with a dashed line in E-R diagram.
What is strong and weak entity set?
the enitity which is set primary key is said to be strong entity and the entity which does not set primary key is said to be weak entity.
Can weak entity be converted into strong entity?
The primary key of a weak entity set is formed by taking the primary key of the strong entity set on which its existence depends (see Mapping Constraints) plus its discriminator. A strong entity set has a primary key. All tuples in the set are distinguishable by that key. A weak entity set has no primary key unless attributes of the strong entity set on which it depends are included. Tuples (a particular row) in a weak entity set are partitioned according to their relationship with tuples in a strong entity set. Tuples within each partition are distinguishable by a discriminator, which is a set of attributes.
How do you convert weak entities to relations?
To convert weak entities to relations in a database schema, you first need to identify the weak entity's identifying relationship with its owner entity. This involves including a foreign key in the weak entity that references the primary key of the owner entity. Additionally, the weak entity should have its own primary key, typically created by combining its partial key with the primary key of the owner entity. Finally, this new relation can be established in the relational schema, ensuring that the weak entity can now be uniquely identified.
When is the concept of weak entity used in data modelling?
A weak entity can be identified uniquely only by considering the primary key of another (owner) entity.
How can you convert weak entity to strong entity?
To convert a weak entity to a strong entity, you can assign it a primary key that uniquely identifies each instance of the weak entity, rather than relying on the primary key of its associated strong entity. This often involves creating a new attribute or a combination of attributes within the weak entity itself to serve as the primary key. Additionally, you may need to remove the dependency on the strong entity's key, ensuring the weak entity can exist independently. Lastly, update the database schema to reflect these changes.
What occurs when a weak entity does not have a candidate key and its instances are indistinguishable without a relationship with another entity?
When a weak entity lacks a candidate key and its instances cannot be uniquely identified without a relationship to another entity, it relies on that relationship to establish its identity. This typically occurs in a one-to-many relationship where the weak entity’s existence is dependent on the strong entity, which provides the necessary identifying attributes. As a result, the weak entity will often include a foreign key from the related strong entity as part of its primary key. Without this relationship, instances of the weak entity would be indistinguishable and cannot be adequately represented in the database.
What is weak entity sets in dbms?
An entity set may not have sufficient attributes to form a primary key is called weak entity set. One with primary key is called strong entity set.
