DATABASES

Databases are organized collections of data designed for electronic storage and retrieval. They provide structured ways to store information and support operations such as querying, updating, and reporting. A database is managed by a database management system (DBMS), which handles storage, transactions, security, and data integrity. Databases rely on a data model and schema that define how data is organized, what types of records exist, and how they relate.

Relational databases organize data into tables of rows and columns, with relationships enforced through keys. SQL is the standard language for querying and modifying data in relational systems. Non-relational databases, or NoSQL systems, include document stores, key-value stores, wide-column stores, and graph databases. These offer flexible schemas and often scale horizontally.

Databases may be centralized or distributed. Distributed databases use replication for availability and sharding or partitioning for scalability. They may be deployed on-premises, in the cloud, or as a service. Core concepts include transactions with ACID properties in traditional systems, or BASE models in some NoSQL designs, as well as indexes to speed lookups, and constraints that enforce data integrity.

Common families include relational DBMS (e.g., PostgreSQL, MySQL, Oracle, SQL Server), document stores (MongoDB), graph databases (Neo4j), and in-memory systems (Redis). Time-series databases optimize for timestamped data.

Databases underpin applications across sectors such as finance, e-commerce, and research, handling data governance, security, backups, and performance tuning.