Relational Database

A relational database is a type of database that stores data in tabular form (columns and rows). Relational databases are based on the relational data model, thus allowing for a consistent method and language of querying: Structured Query Language (SQL). In relational databases, columns hold attributes of data (such as datatype) and rows hold instances called “records.” Relationships can be defined between tables using rules such as foreign key constraints which declare that a value in one table must come from an existing value in a separate table. Tables can be linked together (related) based on common data to support querying across multiple tables.

Relational Database	NoSQL Database
Low flexibility, high structure	High flexibility, low structure
Effective for data storage on a single server	Designed for use across distributed systems
Single query language: SQL	Query language specific to product

Examples

• Microsoft Access
• MySQL
• Oracle DB
• PostgreSQL
• SQLite

Further Resources

• Ahuja & Vasudevan (2022) “Databases and SQL for Data Science with Python”
• Codecademy (2022) “What is a Relational Database Management System?”
• Relational Database (Wikipedia)