What is the difference between Hadoop and a database?

Hadoop is an open-source distributed processing framework used for storing and analyzing large-scale datasets. It stores data across multiple nodes and utilizes the MapReduce algorithm for processing and analyzing the data. Hadoop is suitable for scenarios dealing with unstructured data and large amounts of data, providing high scalability and fault tolerance.

A database is a software system used to store, manage, and query data. It utilizes a structured data model, and ensures transaction support and data consistency. Databases are typically used to store structured and small-scale data sets, offering efficient data access and query capabilities.

Therefore, the main difference between Hadoop and databases lies in the way data is processed and the scenarios in which they are used. Hadoop is suitable for processing unstructured data and large datasets, providing distributed storage and computing abilities, while databases are suitable for storing and managing structured data, offering efficient data access and query capabilities.