Multiplicity. Place multiplicity notations near the ends of an association. These symbols indicate the number of instances of one class linked to one instance of the other class. For example, one company will have one or more employees, but each employee works for one company only.

The number of times a given factor appears in the factored form of the equation of a polynomial is called the multiplicity. The zero associated with this factor, x=2 , has multiplicity 2 because the factor (x−2) occurs twice.

In software engineering, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system’s classes, their attributes, operations (or methods), and the relationships among objects.

To show a composition relationship in a UML diagram, use a directional line connecting the two classes, with a filled diamond shape adjacent to the container class and the directional arrow to the contained class.

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In UML, cardinality is represented by characters: “..1” (meaning that an instance of the first entity class can be associated with no more than one instance of the second class) or “.. *” (meaning that the first entity can be associated with an unlimited number of instances of the second class).

Cardinality can be 1 or Many and the symbol is placed on the outside ends of the relationship line, closest to the entity, Modality can be 1 or 0 and the symbol is placed on the inside, next to the cardinality symbol. For a cardinality of 1 a straight line is drawn.

An entity relationship diagram (ERD) shows the relationships of entity sets stored in a database. By defining the entities, their attributes, and showing the relationships between them, an ER diagram illustrates the logical structure of databases. ER diagrams are used to sketch out the design of a database.

There are three types of relationships between the data you are likely to encounter at this stage in the design: one-to-one, one-to-many, and many-to-many. To be able to identify these relationships, you need to examine the data and have an understanding of what business rules apply to the data and tables.

A weak, or non-identifying, relationship exists if the primary key of the related entity does not contain a primary key component of the parent entity. Company database examples include: Customer(CustID, CustName) Order(OrderID, CustID, Date)

Explanation: Ellipse represents attributes, rectangle represents entity. 6. What is a relationship called when it is maintained between two entities? Explanation: Primary key of one relation used as an attribute in another relation is called foreign key.

A relationship degree indicates the number of entities or participants associated with a relationship. A unary relationship exists when an association is maintained within a single entity. A ternary relationship exists when three entities are associated.

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A many-to-many relationship occurs when multiple records in a table are associated with multiple records in another table. To avoid this problem, you can break the many-to-many relationship into two one-to-many relationships by using a third table, called a join table. …

In a relational database, a weak entity is an entity that cannot be uniquely identified by its attributes alone; therefore, it must use a foreign key in conjunction with its attributes to create a primary key. The foreign key is typically a primary key of an entity it is related to.

Explanation: A relationship is an association among several entities. A relationship specifies how two entities are related. Explanation: A relationship may also have attributes. These attributes are called as descriptive attributes.