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Q: Difference between an entity set and an entity instance?
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Difference between entity and entity set?

Entity - Table Entity Set - Rows in Table


Difference between entity type and entity set?

lets understand them all: 1.An Entity is a real world "thing" which have independent existence. 2.Entity type is a category. 3.entity type is strictly calling, "an instance of entity type". 4.An entity type defines a collection of entities that have the same attributes. 5.Entity set : the collection of all entities of a particular entity type in the database at any point of time is called Entity set.


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.


Diffentiate between an entity and an entity set?

What do you mean by referral integrity constraints ?


What is the difference between insured and insurer?

The insured is the person or entity who is covered by the insurance policy. The insurer is the entity (insurance company)that pays to, or on behalf, of the insured for a covered loss. That which is covered by the policy is set forth in the insurance policy.


What is the difference between program and process?

Program is a set of instruction whereas process is program in execution. Program is passive entity whereas process is active entity .Program has single instance whereas process has several instances.For eg.several notepad windows can be opened but same program is executed behind each window. Program is dependent on logic used whereas process is dependent on program.


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.


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 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.


What is entity classes?

same as entity class or entity type or entity set


A relationship between the instances of a single entity type is called a ........................?

A relationship between instances of a single entity type is called a self-relationship or recursive relationship. This type of relationship occurs when an entity is related to other instances of the same entity type within the same entity set.


What is an extension of an entity type?

its an set of entity