# Set Theory

## About

A set has several interpretation:

- the original set that does not allow duplicate
- the multiset (also known as a bag) that allows duplicate

This section is about what's called the set theory (ie what rules and operations applied to a set of data).

Sets are one of the most fundamental concepts in mathematics. Developed at the end of the 19th century, set theory is now a ubiquitous part of mathematics, and can be used as a foundation from which nearly all of mathematics can be derived.

## Articles Related

## Syntax

{ } are the standard notation for sets.

## Application

The most important application of set theory is the relational theory where a relation (ie a relational table, view) is:

- a set of row (tuple) with unique constraint
- a bag of row (tuple) without unique constraint

And therefore all operations performed on a relation are also set operation.

## Visualisation

Set operations are visualized with venn diagrams