What is a NoSQL database?

NoSQL is a class of database management systems (DBMS) that do not follow all of the rules of a relational DBMS and cannot use traditional SQL to query data. This type of database is not generally a replacement but, rather, a complementary addition to RDBMS and SQL. These databases are used in very large databases.

NoSQL databases are purpose-built for specific data models and have flexible schemas for building modern applications. These databases are widely recognized for their ease of development, functionality, and performance at scale. This page includes resources to help you better understand NoSQL databases and to get started.

For decades, the predominant data model that was used for application development was the relational data model used by relational databases such as Oracle, DB2, SQL Server, MySQL, and PostgreSQL. It wasn’t until the mid to late 2000s that other data models began to gain significant adoption and usage. To differentiate and categorize these new classes of databases and data models, the term “NoSQL” was coined. Often the term “NoSQL” is used interchangeably with “non-relational.”

How Does a NoSQL (non-relational) Database Work?

NoSQL databases use a variety of data models for accessing and managing data, such as document, graph, key-value, in-memory, and search. These types of databases are optimized specifically for applications that require large data volume, low latency, and flexible data models, which are achieved by relaxing some of the data consistency restrictions of other databases.

Consider the example of modeling the schema for a simple book database:

• In a relational database, a book record is often dissembled (or “normalized”) and stored in separate tables, and relationships are defined by primary and foreign key constraints. In this example, the Books table has columns for ISBN, Book Title, and Edition Number, the Authors table has columns for AuthorID and Author Name, and finally the Author-ISBN table has columns for AuthorID and ISBN. The relational model is designed to enable the database to enforce referential integrity between tables in the database, normalized to reduce the redundancy, and generally optimized for storage.

• In a NoSQL database, a book record is usually stored as a JSON document. For each book, the item, ISBN, Book Title, Edition Number, Author Name, and AuthorID are stored as attributes in a single document. In this model, data is optimized for intuitive development and horizontal scalability.

Seems good thing but why should I use a NoSQL database?

NoSQL databases are a great fit for many modern applications such as mobile, web, and gaming that require flexible, scalable, high-performance, and highly functional databases to provide great user experiences.

Schema agnostic: NoSQL databases are schema agnostic. You aren’t required to do a lot on designing your schema before you can store data in NoSQL databases. You can start coding, and store and retrieve data without knowing how the database stores and works internally. If you need advanced functionality, then you can customise the schema manually before indexing the data. Schema agnosticism may be the most significant difference between NoSQL and relational databases.

Scalability: NoSQL databases support horizontal scaling methodology that makes it easy to add or reduce capacity quickly without tinkering with commodity hardware. This eliminates the tremendous cost and complexity of manual sharding that is necessary when attempting to scale RDBMS.

Performance: Some databases are designed to operate best (or only) with specialized storage and processing hardware. With a NoSQL database, you can increase performance by simply adding cheaper servers, called commodity servers. This helps organisations to continue to deliver reliably fast user experiences with a predictable return on investment for adding resources again, without the overhead associated with manual sharding.

High availability: NoSQL databases are generally designed to ensure high availability and avoid the complexity that comes with a typical RDBMS architecture, which relies on primary and secondary nodes. Some ‘distributed’ NoSQL databases use a master less architecture that automatically distributes data equally among multiple resources so that the application remains available for both read and write operations, even when one node fails.

Global availability: By automatically replicating data across multiple servers, data centres or cloud resources, distributed NoSQL databases can minimize latency and ensure a consistent application experience wherever users are located. An added benefit is a significantly reduced database management burden of manual RDBMS configuration, freeing operations teams to focus on other business priorities.