Note: this article is published on 08/17/2024.
This series of articles is about relationship between entity or datasets.
A - Introduction
Previous article, Relations between Dataset in DBMS, discuss the concept of a relationship in DBMS.This article will show the ER Diagram --- Entiry Relationship Diagram. The content of this article:
- A - Introduction
- B - Types of Relationsip in DBMS
- C - Cardinality Diagram
- D - ERD symbols and notations
- Chen notation style
- Crow’s Foot/Martin/Information Engineering style
- Bachman style
- Barker style
- E - Samples
B - Types of Relationsip in DBMS
The three main cardinal relationships are
- One-to-One --- A row in a table is related to only one role in another table and vice versa.
- One-to-Many --- A row from one table can have multiple matching rows in another table.
- Many-to-Many --- A row from one table can have multiple matching rows in another table and vice versa.
C - Cardinality Diagram
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D - ERD symbols and notations
There are several notation systems, which are similar but vary in a few specifics.
Chen notation style
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Crow’s Foot/Martin/Information Engineering style
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Bachman style
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Barker style
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E - Samples
As below:
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References: