Overview
ISO/IEC 9075-9:2023 - commonly called SQL/MED (Management of External Data) - is the international standard that extends SQL to support access to and management of external data sources. The standard defines language constructs, catalog objects, and interfaces needed to integrate foreign servers, foreign-data wrappers, user mappings, and datalink types into SQL-based systems. It standardizes how external data is discovered, referenced, described and manipulated from within SQL environments to improve interoperability and portability across database systems.
Key topics and technical requirements
The standard covers a broad set of functional areas; notable topics include:
- Foreign tables and foreign servers: definitions and catalog operations for registering and managing remote or external tables.
- Foreign-data wrappers (FDWs): the model and foreign-datawrapper interface including initialization, access, termination, error handling and diagnostics.
- User mappings and routinemappings: how credentials and routine behavior map between local SQL sessions and external data sources.
- Datalinks: types and operations for referencing large objects or external resources (URLs, file handles) from SQL.
- SQL language extensions: syntax additions for schema definition, table definition, ALTER/DROP for foreign objects, and session statements (e.g., passthrough).
- Dynamic SQL, embedded SQL and Call-Level Interface (SQL/CLI): rules for descriptors, prepare/execute, and CLI routines that interact with external data.
- Catalog manipulation and import/export: statements for creating, altering and importing foreign schemas and drivers.
- Diagnostics, security and transactions: privileges, basic security model, and transaction properties when external data is involved.
- Detailed interface routines: a comprehensive list of FDW and wrapper routines and their invocation behaviors (connect, fetch, free, diagnostics, etc.).
(These topics are drawn from the standard’s content structure and identify the key technical areas addressed.)
Practical applications
SQL/MED is focused on enabling and standardizing practical use cases such as:
- Federated queries and data virtualization across heterogeneous systems (RDBMS, NoSQL, cloud stores, files, web APIs).
- Integrating remote datasets without ETL by exposing them as foreign tables.
- Linking to large external resources (multimedia, documents) using datalinks.
- Building portable FDW implementations that work across compliant DBMSs.
- Implementing secure credential mappings and controlled passthrough execution to external services.
Who should use this standard
- Database engine developers and vendors implementing SQL/MED support (FDWs, catalogs, CLI).
- Data architects and system integrators designing federated or virtualized data platforms.
- Application developers building SQL-access layers to external sources.
- Standards and compliance teams evaluating interoperability and portability of SQL solutions.
Related standards
ISO/IEC 9075-9:2023 is part of the broader ISO/IEC 9075 (SQL) family and interoperates with SQL/Foundation and SQL/CLI specifications to provide complete external-data management support.
Keywords: ISO/IEC 9075-9:2023, SQL/MED, foreign-data wrapper, datalink types, management of external data, federated queries, database interoperability.
Open preview (PDF)Information technology — Database languages SQL — Part 9: Management of External Data (SQL/MED)
