Data Modeling - Relationships
Table of Contents
1 - About
Order is the most important concept in the modeling as it design the relation between entities.
A relationship is a description that has a verb that relates two entity types:
- consists of
2 - Articles Related
3 - Domain
3.1 - DBMS
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.
3.2 - Between two variables
3.2.1 - Function
A function can also describe a relationship between two variables.
NHST try to find this relation.
3.2.2 - Category
Same category: See Data Modeling - (Taxonomy|Classification)
3.3 - 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.
5 - Binary Relation
6 - Order Relation
Order - Relationship - greater than, …