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Which are the Different symbols used in entity relationship model?
mandatory and optional
A common visual model used to guide the design of a database is known as a?
Entity Relationship Diagram, or ERD.
What type of graphical model is used to define database?
An Entity Relationship Diagram is one graphical method. A dataflow diagram is another way of looking at a system for which you will design a database.
What is aggregation in ER diagram?
-Used when we have to model a relationship involving (entitity sets and) a relationship set.-Aggregationallows us to treat a relationship set as an entity set for purposes of participation in (other) relationships.
What are the difference between Entity Relationship Program and Flow Chart?
ER diagram is Entity Relationship Diagram which shows relationship between different entities in a process.... Data Flow diagram is a symbolic structure which shows the flow of data how it is used in diff stages in a particular process....
What is the ER diagram on water bill system?
ER means that Entity relationship diagram that shows about system interaction on water and sewerage system development.Which is used fast and suficent water bill distribution for customers .
Purpose of Information flow diagram and Entity Relationship diagram.?
Information flow diagram is used to visually represent the flow of information within a system, showing how data is input, processed, and output. Entity Relationship diagram is a visual representation of the relationships between entities in a database, illustrating the structure of the database and how data is organized. Both diagrams help in understanding and designing systems more effectively.
What are the valve symbols used in piping?
Commonly used P&ID symbols (Piping and Instrumentation Diagram symbols) for manual valves.
Why are entity relationship diagrams used?
Entity Relationship (ER) diagrams are drawn when designing a database system, After the systems specification, an ER diagram is drawn showing the conceptual design of the database, this diagram shows the type of information that is to be stored in the system and how these information associate with each other (e.g. one-to-one, one-to-many, etc).ER Diagrams are simple and easy to understand, thus, this diagram can be shown and explained to user representatives for confirmation and approval.use of er diagram
What are the advantages and disadvantages of Entity Relationship Diagrams?
Entity-Relationship diagrams are useful for modelling data and the relationships between the data. They can be used when the constraints between data are relatively simple. They do not allow specification of interactions between the data or model how the data changes (there are no processes in Entity-Relationship). Entity-Relationship diagrams are most often used to model databases.
When do you have to use an intersection entity in database?
If you have a many-to-many relationship between two entities you create an intermediate entity between.Now, the relationship between the first entity and intersection entity is one-to-many, and the relationship between the second entity and intersection entity is one-to-many also.
What is cardinality in an ER diagram?
An E-R diagram may also indicate the cardinality of a relationship. Cardinality is the number of instances of one entity that can, or must, be associated with each instance of another entity. In general we may speak of one-to-one, one-to-many, or many-to-many relationships. There are several different styles used to draw Entity-Relationship diagrams. The Kendall and Kendall text uses the Crow's Foot notation. Using this notation entities are represented by rectanges and relationships are indicated by lines connecting the rectangles. Cardinality is shown by a series of "tick marks" and "crows feet" superimposed on the relationship lines.
