Data Modeling - Relationships
Table of Contents
1 - About
The relationship is the core aspect of a relational database.
All relationships are implicitly bidirectional, meaning that they can interpreted in both directions.
When you have foreign key that NOT references the primary key of another table, the database has not enforced referential integrity.
In a data model, two main relationship are used :
but you can found other types as :
- optional on one side one-to-one
To describe precisely the type of relationship in a data model, you use the cardinality.
A relationship is a description in a business document that has a verb that relates two entity types:
- consists of
2 - Articles Related
3 - Natural Language
In a natural language such as English, there are four primary relationships:
- or time
modelled with the help of preposition.
Verbs provide a link to the condition/state of being of the subject.
coordinating conjunctions indicate the following logical relationship between sentences:
- not another option
- another option
- contrasting addition
Adverbial conjunctions indicate the following logical relationship between two sentences, or phrases.
- Comparison or Contrast
- Cause or Effect
4 - Recursive relation
Pretend the recursive relation is between two tables, the real one and a virtual copy.
In this case, a manager table and an employee table.