What’s the difference between SQL and NoSQL?

 SQL databases are primarily referred to as Relational Databases (RDBMS).

NoSQL databases are primarily referred to as Non-relational or Distributed Database.

SQL

• SQL databases are table based databases.
• Have predefined schema.
• Are vertically scalable.
• Use SQL (Structured Query Language) for defining and manipulating the data. A good fit for the complex query intensive environment
• Emphasize ACID properties (Atomicity, Consistency, Isolation and Durability)
• Examples include: MySql, Oracle, Sqlite, Postgres and MS-SQL.

                                NoSQL

• NoSQL databases are document based, key-value pairs, graph databases.
• Have dynamic schema.
• Are horizontally scalable.
• Focused on the collection of documents.
• Not ideal for complex queries.

• Follow the Brewers CAP theorem (Consistency, Availability and Partition tolerance )

• Examples include: MongoDB, BigTable, Redis, RavenDb, Cassandra, Hbase, Neo4j and CouchDb.

Diving deeper

• Relational database: is a collective set of multiple data sets organized by tables, records and columns.
• Document database: pairs each key with a complex data structure known as a document. Documents can contain many different key-value pairs and nested documents.

• Key-value database: are the simplest NoSQL databases. Every single item in the database is stored as an attribute name (or ‘key’), together with its value.