Database

Relational Database Management System (RDBMS)

A relational database management system (RDBMS) is a program used to create, update, and manage relational databases. Some of the most well-known RDBMSs include

• MySQL
• PostgreSQL
• MariaDB,
• Microsoft SQL Server, and
• Oracle Database

Advantages of Relational database

1. Consistency
   • tables are related to each other
2. Security (because tables are separated)
3. Ease of backup and recovery

See Relational Calculus.

Relational Database Schema

A relational database schema is a pair $⟨\rho ,\Sigma ⟩$, where $\rho$ is a signature, and where $\Sigma$ is a finite set of integrity constraints that are sentences over $\rho$.

Relational Databases and Consistency

A relational database consists of a relational database schema $⟨\rho ,\Sigma ⟩$ and an instance $DB$ of its signature $\rho$.

The relational database is consistent if and only if, for any integrity constraint $\phi \in \Sigma$ and any valuation $\theta$: $DB,\theta \models \phi$

https://cloud.google.com/learn/what-is-a-relational-database