Relational databases, NoSQL databases, and NewSQL databases are all types of databases that are used for storing and managing data, but they have some key differences:

1. Relational databases: Relational databases, such as MySQL, Oracle, and SQL Server, are based on the relational model and use a structured query language (SQL) to store and retrieve data. They store data in tables with rows and columns, and use a schema to define the relationships between the tables. They are best suited for structured data and transactional workloads.
2. NoSQL databases: NoSQL databases, such as MongoDB, Cassandra, and HBase, are designed to handle unstructured and semi-structured data. They do not use a fixed schema, and they often use a key-value, document, graph, or column-family data model. They are designed to scale horizontally and handle high write loads, which makes them ideal for big data and real-time analytics use cases.
3. NewSQL databases: NewSQL databases, such as Google Spanner, CockroachDB, and TiDB, are a new generation of relational databases that combine the scalability and performance of NoSQL databases with the consistency and transactional support of relational databases. They use SQL and provide a relational data model, but unlike traditional relational databases, they can scale horizontally and handle high write.