A relational database is a digital database based on the relational model of data and uses Structured Query Language (SQL) and follows ACID (Atomicity, Consistency, Isolation, Durability) property strictly.
SQL databases have been a primary data storage mechanism for more than four decades. Usage exploded in the late 1990s with the rise of web applications and open-source options such as MySQL, PostgreSQL, and SQLite.
NoSQL or Non-Relational databases have existed since the 1960s, but have recently been gaining traction with popular options such as MongoDB, CouchDB, Redis, and Apache Cassandra. They are a data storage system that was designed for unstructured data which does not follow an ACID property like a traditional RDBMS but follows a property called CAP theorem.
We will explore the difference between SQL and NoSQL in this blog post.
Non-Relational (NoSQL) database vs Relational Database(SQL)
| Name | Relational Database(SQL) | Non-Relational Database (NoSQL) |
|---|---|---|
| Database Model | RDBMS in the form of Tables (row/column) | Graph, Columnar, Key-value pair, Document Wide Column Stores |
| Data Schema | Has Predefined and Strict Schema | Unstructured data and supports flexible Schema |
| Transaction Support | Yes, supports ACID property | No, based on BASE {CAP Theorem} |
| Foreign Keys | Yes | No |
| Query Language | Structured Query Language(SQL) | Unstructured Query Language (UnQL) |
| Data Integrity | Most SQL databases allow you to enforce data integrity rules using foreign key constraints. The schema forces rules for the database to follow | The same data integrity options are not available in the NoSQL database; you can store what you want regardless of any other documents. |
| Joins | SQL queries offer a powerful JOIN clause. We can obtain related data in multiple tables using a single SQL statement. | NoSQL has no equivalent of JOIN |
| Scalability | Vertically Scalable | Horizontal Scalable |
| Examples | MySQL, Oracle, SQLite, Microsoft SQL Server, PostgreSQL | Cassandra, MongoDB, Redis, HBase, Neo4j, CouchDB, RavenDB |
As a relational database supports the table-based structure, it is a better option for applications that needs multi-row transactions such as accounting system.