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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.
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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.
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.
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.
Why do we need weak entity sets?
why do we need weak entity in database when we can make it strong entity?
What is strong entities vs weak entities?
The table that has primary key is strong entity and the table that has no primary key is weak entity
Example of weak entity set?
an entity set may not have sufficient attribute 2 form a primary key is called weak entity set.ex entity set payment has 3 attribute pay-no,pay-date, pay-amount.pay-no is a sequential no generated 4 each loan.each payment entity is distinct,payments 4 different loans may share the same payment no.thus entity set doent have a primary key,so it is a weak entity set. Placid04 bakhra,muzaffarpur,bihar.
Why do you need weak entity set?
the entity set departure which has only one attribute date is a weak entity set. this is because if each departure entity is distinct, different flights may have departure on same day, so different flights may share the same date valuebbye
Examples of weak entity?
an entity set may not have sufficient attribute 2 form a primary key is called weak entity set.ex entity set payment has 3 attribute pay-no,pay-date, pay-amount.pay-no is a sequential no generated 4 each loan.each payment entity is distinct,payments 4 different loans may share the same payment no.thus entity set doent have a primary key,so it is a weak entity set. Placid04 bakhra,muzaffarpur,bihar.
What two conditions must be met before an entity can be classified as a weak entity?
In contrast to the strong or regular entity, a weak entity is one that meets two conditions: 1. The entity is existence-dependent; that is, it cannot exist without the entity with which it has a relationship. 2. The entity has a primary key that is partially or totally derived from the parent entity in the relationship.
What is the difference between a required attributes and optional attributes?
strong entity : in this the attributes must have values for instance . weak entity : in this the attributes may or may not have values for instance .
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.
