NoSQL vs. SQL

When talking about SQL databases, we also have to mention the elephant in the room: NoSQL.

To put it simply, a NoSQL database is a database that does not use SQL (Structured Query Language). Each NoSQL typically has its own way of writing and executing queries. For example, MongoDB uses MQL (MongoDB Query Language) and ElasticSearch simply has a JSON API.

While most relational databases are fairly similar, NoSQL databases tend to be fairly unique and are used for more niche purposes. Some of the main differences between SQL and NoSQL databases are:

NoSQL databases are usually non-relational, SQL databases are usually relational (we'll talk more about what this means later).
SQL databases usually have a defined schema, NoSQL databases usually have dynamic schema.
SQL databases are table-based, NoSQL databases have a variety of different storage methods, such as document, key-value, graph, wide-column, and more.

Types of NoSQL Databases

A few of the most popular NoSQL databases are:

Which type of database always uses table structures?