Subject: Databases What role does the entity-relationship (ER) diagram play in t
ID: 3676155 • Letter: S
Question
Subject: Databases
What role does the entity-relationship (ER) diagram play in the design process? Discuss the different types of information represented in the ER diagram and the symbols used to represent them. Discuss the meaning of an entity as related to ER diagrams. How would you approach the diagramming process?
When designing database tables, the difference between a good design and a bad design can be a few seconds in response time and several minutes. You may think that this is not a huge difference, but imagine waiting several minutes on a web page for your results to load. How long would you wait? A slow database can mean the loss of customers. So let's begin by discussing some of the common elements of tables and how you would approach the table design. What would you do to ensure that your page loads in a few seconds? Discuss the relationship types and how they affect your design.
Explanation / Answer
An entity-relationship diagram (ERD) is a graphical representation of an information system that shows the relationship between people, objects, places, concepts or events within that system. An ERD is a data modeling technique that can help define business processes and can be used as the foundation for a relational database
While useful for organizing data that can be represented by a relational structure, an entity-relationship diagram can't sufficiently represent semi-structured or unstructured data, and an ERD is unlikely to be helpful on its own in integrating data into a pre-existing information system.
Three main components of an ERD are theentities, which are objects or concepts that can have data stored about them, the relationship between those entities, and the cardinality, which defines that relationship in terms of numbeThe three main cardinal relationships are:
ER diagram is the actual blueprint of the database. Its composition must reflect an organization's operations accurately if the database is to meet that organization's data requirements. It forms the basis for a final check on whether the included entities are appropriate and sufficient, on the attributes found within those entities, and on the relationships between those entities. It is also used as a final crosscheck against the proposed data dictionary entries. ER diagram also lets the designer communicate more precisely with those who commissioned the database design. Finally, the completed ER diagram serves as the implementation guide to those who create the actual database. In short, the ER diagram is as important to the database designer as a blueprint is to the architect and builder.
ENTITIE symbols are generally used for conceptual data models, although some aspects may spill over into logical data models. They can be found in the UML Entity Relationship and Entity Relationship shape libary of Lucidchart. If you don't see the shape you need, use an image file (Lucidchart supports .PNG, .JPG, or .SVG import) or create your own with our existing shapes and styling options.
Entities are objects or concepts that represent important data. They are typically nouns, e.g. customer, supervisor, location, orpromotion.
Database design is the process of producing a detailed data model of a database. This data model contains all the needed logical and physical design choices and physical storage parameters needed to generate a design in a data definition language, which can then be used to create a database. A fully attributed data model contains detailed attributes for each entity. n relational databases and flat file databases, a table is a set of data elements (values) using a model of vertical columns (identifiable by name) and horizontal rows, the cell being the unit where a row and column intersect. A table has a specified number of columns, but can have any number of rows.
A well-designed database shall: