A NoSQL database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. SQL databases have constraints on data types and consistency. NoSQL does away with them for the sake of speed, flexibility, and scale.
Multi-Model Where relational databases require data to be put into tables and columns to be accessed and analyzed, the various data model capabilities of NoSQL databases make them extremely flexible when it comes to handling data. They can ingest structured, semi-structured, and unstructured data with equal ease, whereas relational databases are extremely rigid, handling primarily structured data.
Easily Scalable It’s not that relational databases can’t scale, it’s that they can’t scale EASILY or CHEAPLY, and that’s because they’re built with a traditional master-slave architecture, which means scaling UP via bigger and bigger hardware servers as opposed to OUT or worse via sharding. Sharding means dividing a database into smaller chunks across multiple hardware servers instead of a single large server, and this leads to operational administration headaches.
Flexible Where relational databases require data to be put into tables and columns to be accesses and analyzed, the multi-model capabilities of NoSQL databases make them extremely flexible when it comes to handling data.
Distributed NoSQL database that is designed to distribute data at global scale, meaning it can use multiple locations involving multiple data centers and/or cloud regions for write and read operations. Relational databases, in contrast, use a centralized application that is location-dependent (e.g. single location), especially for write operations.
Zero Downtime The final but certainly no less important key feature to seek in a NoSQL database is zero downtime. This is made possible by a masterless architecture, which allows for multiple copies of data to be maintained across different nodes.
Key-Value Store – It has a Big Hash Table of keys & values Document-based Store- It stores documents made up of tagged elements. Column-based Store- Each storage block contains data from only one column. Graph-based-A network database that uses edges and nodes to represent and store data.