What does dotted underline mean in ERD?
Weak Key ElementThe ER diagram you included seems to be using a variant of Chen's notation. In that notation form, the double outline indicates a dependent element (i.e. You can't have a book without an author writing it). The dashed underline represents a Weak Key Element.
What is dotted oval in ER diagram?
In ER diagram, derived attribute is represented by dashed oval. Relationship Type and Relationship Set: 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.
What does dotted line mean in SQL?
The dotted/dashed line means, that SQL Server does not enforce referential integrity for this relationship.
What does thick line mean in ER diagram?
a thick line indicates both, i.e. bijectivity: each entity in the entity set is involved in exactly one relationship. an underlined name of an attribute indicates that it is a key: two different entities or relationships with this attribute always have different values for this attribute.
What is double line in ER diagram?
The relationship between one strong and a weak entity set shown by using the double diamond symbol. The connecting line of the strong entity set with the relationship is single. The line connecting the weak entity set for identifying relationship is double.
What are the symbols used in ER?
More Questions About ER Diagram Symbols There are 3 commonly used symbols in entity relationship diagram – Entity, Relationship, and Attribute.
What do you mean by referential integrity take example to explain?
Referential integrity It means the reference from a row in one table to another table must be valid. Examples of referential integrity constraint in the Customer/Order database of the Company: Customer(CustID, CustName) Order(OrderID, CustID, OrderDate)
What column uniquely identifies each row in a database table?
the primary keyIn the relational model, each table schema must identify a column or group of columns, called the primary key, to uniquely identify each row.
What is double line and single line in ER diagram?
Participation Constraints Total Participation − Each entity is involved in the relationship. Total participation is represented by double lines. Partial participation − Not all entities are involved in the relationship. Partial participation is represented by single lines.
Which attributes are depicted by dashed ellipse?
Derived attributes are depicted by dashed ellipse.
What are constraints in ER diagram?
Constraints are used for modeling limitations on the relations between entities. Mapping cardinality or cardinality ratio. Participation constraints.
How can you tell if a entity is strong or weak?
Difference between Strong and Weak Entity:Strong entity always has a primary key. While a weak entity has a partial discriminator key.Strong entity is not dependent on any other entity. ... Strong entity is represented by a single rectangle. ... Two strong entity's relationship is represented by a single diamond.
What is a weak entity in ER diagram?
A weak entity is a type of entity which doesn't have its key attribute. It can be identified uniquely by considering the primary key of another entity. For that, weak entity sets need to have participation. In above ER Diagram examples, “Trans No” is a discriminator within a group of transactions in an ATM.
What is weak relationship in ER diagram?
A weak or non-identifying relationship exists between two entities when the primary key of one of the related entities does not contain a primary key component of the other related entities.
What is partial key in ER diagram?
Partial Key : The set of attributes that are used to uniquely identify a weak entity set is called the Partial key. Only a bunch of the tuples can be identified using the partial keys. The partial Key of the weak entity set is also known as a discriminator.
What is a dotted line in an organization chart?
Lines in an organization chart can be in the form of solid lines or dotted lines. A dotted line is also called a broken line or a dashed line. They represent different types of reporting relationships. The line's weight is meant to represent the level of power and influence of the different managers.
What is a solid line?
Part 1: Solid and Dotted Line Reporting Relationship 1 The solid line reporting relationship is similar to a traditional line management role. The solid line manager tends to look after the goal setting and performance evaluation processes. In the event of a dispute, individuals will tend to defer to this manager. The solid line role is often given to either the functional manager or a manager who is geographically close to the individual, which is to make supervision easier. 2 The dotted line relationship is weaker than solid line relationship. The dotted line manager still has rights to certain parts of the individual's time and attention and usually set some goals.
Is a dotted line relationship weaker than a solid line relationship?
In the event of a dispute, individuals will tend to defer to this manager. The solid line role is often given to either the functional manager or a manager who is geographically close to the individual, which is to make supervision easier. The dotted line relationship is weaker than solid line relationship.
Entity
Entities are represented by means of rectangles. Rectangles are named with the entity set they represent.
Attributes
Attributes are the properties of entities. Attributes are represented by means of ellipses. Every ellipse represents one attribute and is directly connected to its entity (rectangle).
Relationship
Relationships are represented by diamond-shaped box. Name of the relationship is written inside the diamond-box. All the entities (rectangles) participating in a relationship, are connected to it by a line.
What is an ER model?
Creating an entity-relationship (ER) model is to visually represent the structure of a business database, where data equates to entities (or objects) that are linked by defined relationships expressing dependencies and requirements. By nature it is an abstract visualization, the first step in the design process towards creating a logical and functional database.
What does a flow line mean?
Flow Line ... An arrow coming from one symbol and ending at another symbol represents that control passes to the symbol the arrow points to. The line for the arrow can be solid or dashed. The meaning of the arrow with dashed line may differ from one flowchart to another and can be defined in the legend.". [Flowchart.
What is ConceptDraw diagram?
With ConceptDraw DIAGRAM, you can quickly and easily create any type of orgchart professional. ConceptDraw DIAGRAM includes numerous organizational chart templates for the simple to complex multi-page charts.
What is Chen's ERD?
The Chen's ERD notation is still used and is considered to present a more detailed way of representing entities and relationships. To create an ERD, software engineers mainly turn to dedicated drawing software, which contain the full notation resources for their specific database design - ERD symbols and meanings.
What is Garrett IA diagram?
Garrett IA diagrams are used at development of Internet-resources, in particulars at projecting of interactions of web-resource elements. The diagram of information architecture of the web resource which is constructed correctly with necessary details presents to developers the resource in comprehensible and visual way.
What is Crow's foot diagram?
Crow's foot diagrams represent entities as boxes, and relationships as lines between the boxes. Different shapes at the ends of these lines represent the cardinality of the relationship.
What is a business process flow diagram?
Business Process Flow Diagram is a graphical presentation of business processes and process flows. It is one of the main tool of business analysis and business process re-engineering that lets identify and easy understand process flows within organization.
