SQL
SQL
SQL (Structured Query Language) is a domain-specific language designed for managing data held in a relational database management system (RDBMS). Originally developed in the early 1970s by Donald D. Chamberlin and Raymond F. Boyce at IBM, SQL became the standard language for relational database operations. It is used for querying, updating, inserting, and deleting data, as well as for defining and modifying database schemas.
SQL dialects vary among vendors, but the core syntax is standardized by the American National Standards Institute (ANSI) and the International Organization for Standardization (ISO). Common implementations include MySQL, PostgreSQL, SQLite, Microsoft SQL Server, and Oracle Database.
Features
- Data Query Language (DQL) – The most well-known function, using the SELECT statement to retrieve data from tables.
- Data Manipulation Language (DML) – Commands such as INSERT, UPDATE, and DELETE for modifying data.
- Data Definition Language (DDL) – Creating, altering, and dropping database objects with CREATE, ALTER, and DROP.
- Data Control Language (DCL) – Granting and revoking permissions via GRANT and REVOKE.
- Transactional Control – Commands like BEGIN, COMMIT, and ROLLBACK ensure atomicity and consistency.
- Set-based operations – SQL operates on sets of records, making it powerful for batch processing.
SQL also supports complex queries with joins, subqueries, aggregation (GROUP BY, HAVING), and window functions. Many RDBMS extend SQL with procedural language features (e.g., PL/SQL, T-SQL) for stored procedures and triggers.
History
SQL was originally called SEQUEL (Structured English Query Language) and was developed at IBM's San Jose Research Laboratory in the early 1970s. The first commercial implementation was in Oracle Database (released in 1979) by Relational Software (now Oracle Corporation). IBM released its own System R product later. The ANSI SQL standard was first published in 1986, followed by major revisions: SQL-89, SQL-92, SQL:1999 (adding recursive queries and object-relation features), SQL:2003 (XML support and window functions), SQL:2008, SQL:2011 (temporal data), and SQL:2016 (JSON support). SQL remains the dominant language for relational databases, though NoSQL systems have emerged for non-relational data.