0
What else can I help you with?
What are the four main elements in a relation database?
The four main elements in a relational database are tables, rows, columns, and relationships. Tables store data in a structured format, with each table representing a specific entity. Rows (or records) contain individual entries or instances of the entity, while columns (or fields) define attributes of the entity. Relationships establish connections between tables, enabling data integrity and efficient querying across different data sets.
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.
Entity type vs entity instance?
Entity Type : A collection of entities that share common properties or characteristics. for example student is an entity type with common attributes such as student_ID , Name, Class etc. These characteristics are common to all students. Entity Instance: A single occurrence of a particular entity type is called entity instance..
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.
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.
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 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 cardinality ratio in ER diagram?
It specify the number of relationship instances that an entity can participate in.
1An attribute which can be used to uniquely identify the individual instances of the entity is?
Primery Key.
What does the cardinality ratio specify?
The cardinality ratio specifies the number of relationship instances that an entity can participate in.
What is Minimum and Maximum Cardinality?
Minimum and maximum cardinality refer to the constraints on the number of instances of one entity that can be associated with instances of another entity in a relational database or entity-relationship model. Minimum cardinality specifies the least number of instances required, such as "zero" (optional) or "one" (mandatory), while maximum cardinality indicates the upper limit, such as "one" (single instance) or "many" (multiple instances). Together, these concepts help define the nature of relationships between entities, ensuring that data integrity is maintained in the database design.
What is the name of a common database?
it describes the instance of one entity is associated with each instances of an entity depending upon the range of cardinality constraints are two types they are minimum cardinality maximum cardinality
Difference between an entity set and an entity instance?
An entity set is a collection of similar entities that share common attributes, representing a specific concept within a database, such as "Students" or "Employees." In contrast, an entity instance refers to a single, specific occurrence of an entity within that set, encompassing the actual data for a particular individual, like "John Doe" or "Employee ID 12345." Essentially, an entity set is a blueprint or template, while entity instances are the concrete realizations of that blueprint.
When the PK of one entity does not contain the PK of a related entity the relationship is?
When the primary key (PK) of one entity does not contain the primary key of a related entity, the relationship is typically a "one-to-many" or "many-to-many" relationship. In this scenario, the primary key of the first entity can exist independently of the second entity, indicating that multiple instances of the related entity can correspond to a single instance of the first entity. This structure allows for more flexible data modeling where entities can be associated without strict dependency on each other's primary keys.
What is total participation in database management?
Participation (or optionality) concerns the involvement of entities i a relationship. Participation is about exceptions to the rule. An entity's participation is optional if there is a least one instance of an entity which does not participate in the relationship. An entity participation is mandatory if all instances of an entity must participate in the relationship.
What is mapping cardinality?
Mapping cardinality refers to the relationship between two sets in terms of how many elements from one set are associated with elements in another set. It is commonly used in database design and entity-relationship modeling to specify the number of instances of one entity that can or must be associated with instances of another entity. Cardinality can be classified as one-to-one, one-to-many, or many-to-many, affecting how data is structured and accessed. Understanding mapping cardinality is crucial for ensuring data integrity and optimizing database performance.
What are the purpose of business organization?
The purposes of business organizations extend to the establishment of procedure and structure to entities and individuals involved in commercial pursuits. Commercial entities and the individuals that operate them are subject to specific law, by application of a particular commercial entity structure to a commercial entity. The specific type of commercial entity organization also serves in some instances to facilitate the simplification of the application of tax law to the commercial entity.
