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

Hasibul khan

 What is an ERD?

Entity relationship diagram is what it stands for. These diagrams are also known as entity relationship models and ER diagrams. An ERD shows how entities in a database, such as people, things, or concepts, are related to one another. Moreover, an ERD will frequently depict the characteristics of these organizations. An ER diagram can be used to display the relationships between entities, their properties, and the entities themselves to demonstrate the logical structure of databases. This is helpful for engineers who want to document an existing database or develop a new database. (SmartDraw, 2023)

Example this one



(SmartDraw, 2023)




Define the RED-related terms

I diagrammi delle relazioni tra entità offrono un punto di partenza visivo per l'architettura del database e possono anche essere utilizzati per aiutare a identificare le esigenze dei sistemi informativi di un'organizzazione. Un ERD può ancora essere utilizzato come riferimento dopo che un database relazionale è stato distribuito nel caso in cui sia necessario un ulteriore debug o reingegnerizzazione dei processi aziendali. L'organizzazione dei dati che possono essere rappresentati da una struttura relazionale può essere aiutata da un ERD, ma i dati semi-strutturati o non strutturati non possono essere ben rappresentati da esso. Inoltre, è improbabile che sia utile per integrare i dati in un sistema informativo già esistente da solo.(Biscobing, 2019)

(Biscobing, 2019)

cardinalities and relationships

Relationships exist between two query subjects or between tables within a query subject. The cardinality of a relationship is the number of related rows for each of the two objects in the relationship. The rows are related by the expression of the relationship; this expression usually refers to the primary and foreign keys of the underlying table ( IBM, 2023)


Tableau Cardinality Settings in Relationships

There are three types of settings you can have active for cardinality.

One-to-one: When both fields being related have no duplicates – Tableau doesn’t have to do any aggregation at the data source level (least process heavy). (Ramos, 2023)

(Ramos, 2023)

Many-to-one or One-to-many: One field has duplicates and the other has no duplicates – Tableau only has to aggregate data at the source level of one field. (Ramos, 2023)


(Ramos, 2023)

Many-to-many: Both fields have duplicates (or you’re not too sure about the dataset) – Tableau will intuitively aggregate data at the source level for both fields if need be (most process heavy).  This will always be the default when creating relationships and is the safest one to use.(Ramos, 2023)

(Ramos, 2023)





reference

Biscobing, J. (2019) What is entity relationship diagram (ERD)?: Definition from TechTarget, Data Management. TechTarget. Available at: https://www.techtarget.com/searchdatamanagement/definition/entity-relationship-diagram-ERD (Accessed: March 11, 2023).

 IBM (2023) Cardinality, IBM. Available at: https://www.ibm.com/docs/en/cognos-analytics/10.2.2?topic=relationships-cardinality (Accessed: March 11, 2023).

Ramos, M. (2023) The data school - cardinality in Tableau Relationships, The Data School RSS. Available at: https://www.thedataschool.co.uk/marcelo-ramos/cardinality-in-tableau-relationships (Accessed: March 11, 2023).

SmartDraw (2023) Entity relationship diagram (ERD), Entity Relationship Diagram (ERD) - What is an ER Diagram? Available at: https://www.smartdraw.com/entity-relationship-diagram/ (Accessed: March 11, 2023). 


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