What is an ERD. Define the RED related terms, including entities, attributes, cardinalities and relationships

 

Definition of an ERD

 Entity Relationship Diagram, or ER Diagram for short, is a diagram that shows the connections between entity groups that are kept in databases. To put it another way, ER diagrams assist in describing the rational organization of databases. Three fundamental ideas are used to make ER diagrams: things, characteristics, and connections (Peterson, 2022)

RED related terms:

ENTITY:

An entity, which stores data in the database, can be a location, person, object, event, or concept. Entity characteristics must have a property and a distinctive key. Each "attribute" that makes up an entity serves to symbolize it.

ATTRIBUTE:

It is either a single-valued entity or relationship type attribute.

RELATIONSHIP:

The definition of a relationship is simply the association of two or more things. Tom, for instance, works in the Chemistry division.

CARDINALITY:

The definition of the word "cardinality" differs marginally in the context of databases, though. Cardinality in SQL denotes the number of unique elements in a set as opposed to counting the number of elements in a set, which would be similar to counting the number of rows in a table.

Cardinality in databases, however, is not just applicable to the whole array. The column number determines the cardinality. This is so because the number of distinct elements in a database is represented by cardinality. As a result, each column may have a different cardinality due to the possibility that it contains a different number of distinct components. (Gheorghiu, 2021)



Reference(s)
Peterson, R. (2022) Entity relationship (ER) diagram model with DBMS example, Guru99. Available at: https://www.guru99.com/er-diagram-tutorial-dbms.html (Accessed: March 5, 2023).

Gheorghiu, R. (2021) What does cardinality mean in a database? Vertabelo Data Modeler. Vertabelo. Available at: https://www.vertabelo.com/blog/cardinality-in-database/ (Accessed: March 5, 2023).







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