andmebaasid

Andmebaasid, or databases, are structured collections of data stored and managed by a database management system (DBMS). They enable efficient storage, retrieval, and updating of information used by software applications, websites, and other systems. A database organizes data according to a data model, which defines how data is structured and related.

The most common data models are relational and NoSQL. Relational databases store data in tables with rows and columns, using a schema that defines tables, fields, and relationships. NoSQL databases cover a range of models, including document stores that hold semi-structured documents, key-value stores for simple pairs, column-family stores for wide tables, and graph databases that model entities and their relationships. In addition, there are in-memory databases for fast access and time-series databases optimized for timestamped data.

A DBMS provides mechanisms for data definition, access control, querying, and transaction management. Queries are often written in SQL for relational databases, while NoSQL systems offer their own query languages or APIs. Transactions follow ACID properties (Atomicity, Consistency, Isolation, Durability) in many traditional systems, though some NoSQL solutions relax these guarantees for scalability.

Architectures vary from single-node installations to distributed, replicated, and cloud-based deployments. Techniques such as replication, sharding, and clustering improve availability, fault tolerance, and performance. Common use cases include transactional processing, content management, analytics, real-time monitoring, and IoT data collection.

Examples of well-known systems include MySQL, PostgreSQL, Oracle Database, and Microsoft SQL Server (relational); MongoDB, Couchbase (document); Redis (key-value); Cassandra (column-family); and Neo4j (graph). Databases operate under privacy and security requirements such as GDPR in Europe.