mirror of
https://github.com/jackyzha0/quartz.git
synced 2025-12-31 00:34:05 -06:00
24 lines
519 B
Markdown
24 lines
519 B
Markdown
---
|
|
title: "ER-Diagram"
|
|
aliases:
|
|
tags:
|
|
- cosc203
|
|
---
|
|
|
|
|
|
Entity: a thing in the real world with *independent existence* (phsyical e.g., person or conceptual e.g., job)
|
|
Entity type: A collection of entities
|
|
|
|
Attribute: properties of entity
|
|
Attibute types:
|
|
- simple/composite
|
|
- single/multi valued
|
|
- stored/derived
|
|
- key (simple or composite)
|
|
|
|
Relationship: when one entity refers to another
|
|
Relationship type: a set of relationships with the same entity types
|
|
- relationships can have attributes
|
|
- relationships haveL
|
|
|