Can 2 Entities Have More Than One Relationship?

There can be a number of different relationships between the same two entities

. For example: Employee is assigned to a Project, … One entity can participate in a number of different relationships involving different entities.

How many relationships can an entity have?

There are

three types

of relationships that can exist between two entities.

Can two weak entities have a relationship?

1 Answer. It’s

certainly possible

. Consider the following ER diagram in which invoices are composed of lines, and receipts are decomposed into corresponding lines which are allocated to invoice lines. Multiple receipt lines can be allocated to the same InvoiceLine.

How many relationships can be established in an ER diagram?

Three Types

of Relationships in an ERD Diagram

There are three types of relationships that can exist between two entities.

Can an entity connect to another entity?

Each entity has a number of attributes (columns). Within an ERD, an entity set represents an object and the attributes represent that object’s fields. An attribute is never linked to an entity via a relationship.

A relationship links two entities

.

When relation between two entities is treated as a single entity then it is referred as?

Aggregration

. Aggregration is a process when relation between two entities is treated as a single entity.

What is the relationship between entities?

In a relational database a relationship between entities is implemented by

storing the primary key of one entity as a pointer

or “foreign key” in the table of another entity. There is a tradition for ER/data models to be built at two or three levels of abstraction.

What two conditions must be met before an entity can be classified as a weak entity give an example of both a strong and weak entity?

A strong or identifying relationship is when the primary key of the related entity contains the primary key of the “parent”. An entity is weak when two conditions are met:

The entity is existence-dependent on another entity. The entity gets at least part of its primary key from that other entity.

What two conditions must be met before an entity can be classified as a weak entity Give an example of a weak entity?

In any case, two conditions must be met before an entity can be classified as weak:

1. The entity must be existence-dependent on its parent entity 2. The entity must inherit at least part of its primary key from its parent entity.

Can a weak entity have subtypes?

There are two types of weak entities:

associative entities and subtype entities

. … The latter represents a crucial type of normalization, where the super-type entity inherits its attributes to subtype entities based on the value of the discriminator.

How do you identify a many-to-many relationship?

A many-to-many relationship occurs

when multiple records in a table are associated with multiple records in another table

. For example, a many-to-many relationship exists between customers and products: customers can purchase various products, and products can be purchased by many customers.

What is a relationship a one to many relationship?

In relational databases, a one-to-many relationship occurs

when a parent record in one table can potentially reference several child records in another table

. … The opposite of a one-to-many relationship is a many-to-many relationship, in which a child record can link back to several parent records.

Can you join 2 tables to create a many-to-many relationship?

When you need to establish a many-to-many relationship between two or more tables, the simplest way is to

use a Junction Table

. A Junction table in a database, also referred to as a Bridge table or Associative Table, bridges the tables together by referencing the primary keys of each data table.

What are the two ways in which entities can participate in a relationship?

Total and partial

are the two ways that entities can participate in a relationship.

Can entities be attributes?

Entities are

represented by means of their properties

, called attributes. All attributes have values. For example, a student entity may have name, class, and age as attributes.

What is a relationship in entity relationship diagram?

A relationship type

represents the association between entity types

. For example,’Enrolled in’ is a relationship type that exists between entity type Student and Course. In ER diagram, relationship type is represented by a diamond and connecting the entities with lines.

Which one of the following the multiple lower entities are grouped or combined together to form a single higher level entity?

Generalization

is a bottom-up approach in which multiple lower-level entities are combined to form a single higher-level entity. Generalization is usually used to find common attributes among entities to form a generalized entity.

How do you create a relationship between two tables in Entity Framework?

You can create such a relationship by

defining a third table

, called a junction table, whose primary key consists of the foreign keys from both table A and table B.

What do you mean by one-to-many relationship between teacher and?

Answer: Explanation: In a “class roster” database, a teacher may teach zero or more classes, while a class is taught by one (and only one) teacher. This kind of relationship is known as

one-to-many

. … The one-to-many relationship cannot be represented in a single table.

Which of the following is used to represent the relationships between two relations tables )?

Foreign key

is used to represent the relationship between two tables.

When one entity from a can be associated with more than one entity from B then it is called?

Explanation:

Mapping cardinality

is also called as cardinality ratio. Explanation: Here one entity in one set is related to one one entity in other set. 3. An entity in A is associated with at most one entity in B.

What is entity and entity set?

An entity is an object that exists and is distinguishable from other objects. … An entity set is

a set of entities of the same type

(e.g., all persons having an account at a bank). Entity sets need not be disjoint.

What two conditions must be met before an entity can be classified as a weak entity quizlet?

Terms in this set (11) What two conditions must be met before an entity can be classified as a weak entity?

The entity must be existence-dependent on its parent entity. The entity must inherit at least part of its primary key from its parent entity.

How is a relationship between two entities indicated in a crow’s foot ERD?

Instead, the Crow’s Foot ERD uses relationship types –

strong or weak

– to indicate the nature of the relationships between entities. For example, a strong relationship indicates the existence of a weak entity. The entity must inherit at least part of its primary key from its parent entity.

Can a weak entity have two strong 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 two attributes must be contained in the composite entity?

The composite entity must at least include

the primary keys of the (parent) entities it references

B. The composite entity must at least include the foreign keys of the (parent) entities it references.

Can weak entity have primary key?

As

the weak entities do not have any primary key

, they cannot be identified on their own, so they depend on some other entity (known as owner entity). The weak entities have total participation constraint (existence dependency) in its identifying relationship with owner identity.

Is a subtype an entity?

A supertype is a generic entity type that has a relationship with one or more subtypes. A subtype is a

sub-grouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other

subgroups.

Can a weak entity have two parents?

1 Answer. “Can a subclass have 2 parents(2 entities that connect to it?)”.

Yes

.

Which of the following defines an entity?

An entity is

any singular, identifiable and separate object

. It refers to individuals, organizations, systems, bits of data or even distinct system components that are considered significant in and of themselves.

What relationship exists when three entities are associated?

A ternary relationship

exists when three entities are associated.

How many relationships are possible between two tables or entities?

There are

three types

of relationships that can exist between two entities.

What is wrong with many-to-many relationship?

A many-to-many relationship is an intersection of two entities. A person may own stock in multiple companies. … As a result programmers have to use

workarounds

to handle many-to-many relationships in their code. Sometimes they make the bad decision to contaminate a database with their programming representation.

What is the difference between a one-to-many relationship and a many-to-many relationship?

In a One-To-Many relationship, one object is the “parent” and one is the “child”. The parent controls the existence of the child. In a Many-To-Many,

the existence of either type is dependent on something outside the both of them

(in the larger application context).

What is an everyday example of a one-to-many relationship?

Here are some other examples of one-to-many relationships:

People-Addresses

(Each person can live at one address, but each address can house one or more people.) Owners-Pets (Each pet has one owner, but each owner can have one or more pets.)

What is an example of a many to one relationship?

For example, if one department can employ for several employees then,

department to employee

is a one to many relationship (1 department employs many employees), while employee to department relationship is many to one (many employees work in one department).

What shows a many to one relationship?

A many-to-one relationship is where one entity (typically a column or set of columns) contains values that refer to another entity (a column or set of columns) that has unique values. … The key point is that

each city exists in exactly one state

, but a state may have many cities, hence the term “many-to-one.”

How do you normalize a one-to-many relationship?

Which are the two ways in which entities can participate in a relationship a passive and active B simple and complex C total and partial D All of the above?

What is a relationship is called when an association is maintained between two entities?

A relationship is an association that exists between two entities. … Some relationships involve only one entity. For example, Employee reports to Employee: This type of relationship is called a

recursive relationship

. There can be a number of different relationships between the same two entities.

Which forms has a relation that possesses data about an individual entity?