SQL

SQL (Structured Query Language) is a domain-specific programming language designed for managing, manipulating, and querying relational databases. It provides a standardised method for interacting with structured data through commands that allow users to retrieve (SELECT), insert (INSERT), update (UPDATE), and delete (DELETE) records stored in database tables.

SQL operates on the principles of relational algebra and is used in relational database management systems (RDBMS) such as MySQL, PostgreSQL, Microsoft SQL Server, and Oracle Database. The language supports:

• Data Definition Language (DDL) – for creating and modifying database schemas (CREATE, ALTER, DROP)
• Data Manipulation Language (DML) – for data handling (SELECT, INSERT, UPDATE, DELETE)
• Data Control Language (DCL) – for access control (GRANT, REVOKE)
• Transaction Control (TCL) – for managing database transactions (COMMIT, ROLLBACK)

SQL enables the use of joins, aggregations, subqueries, and conditions to process complex queries across interrelated tables.

SQL is widely used in:

• Software development – for back-end data access and integration
• Business intelligence and analytics – to query large datasets for reporting
• Data engineering and warehousing – for transforming and loading structured data
• ERP and CRM systems – where transactional data is managed relationally

Thanks to its structured nature, SQL allows for clear, efficient querying and ensures data consistency across critical business systems.

See also: IoT, Real-time monitoring