SQLstandardin

SQLstandardin is the standardized specification of the SQL language published by ISO/IEC as part of ISO/IEC 9075. It defines the canonical grammar and semantics for querying and modifying relational data, managing transactions, defining schemas, enforcing access control, and interacting with external routines. The standard is designed to promote portability of database applications across vendors and platforms while providing a common foundation for advanced features.

The SQL standard has evolved through multiple revisions since its inception. Notable editions include SQL-92, SQL:1999, SQL:2003, SQL:2008, SQL:2011, and SQL:2016, with further amendments and additional parts over time. Each revision adds capabilities such as enhanced join syntax, common table expressions, window functions, recursive queries, new data types, and procedural extensions under SQL/PSM or related mechanisms. The standard comprises core language elements as well as optional parts that vendors may implement.

Conformance and practical usage. Conformance levels specify the features a database management system must implement to claim ISO SQL compatibility. In practice, major RDBMS implement a substantial subset of ISO SQL, often supplemented by vendor-specific extensions and dialects (for example Oracle's PL/SQL, Microsoft's T-SQL, and PostgreSQL’s procedural features). Because of differences in implementation, portability is best achieved by focusing on core ISO features and by testing code across systems.

Governance and impact. The standard is developed by ISO/IEC JTC1/SC32 and maintained through working groups to support data interoperability, cross-vendor compatibility, and reliable data management. While widely adopted as a reference, many systems combine the ISO SQL standard with proprietary features, influencing portability, performance, and long-term maintenance.