Many DBMSs support the ISO-standardized version of Structured Query Language (SQL): a language for querying and updating relational databases. Together with the Data Definition Language, used to define and modify schemas, the contents of a database can be stored as a collection of schema and data statements.
The language rarely changes, but the various modifications and additions may change along with software updates. If extensions are used, the documentation must show which SQL version is used.
It is possible to refer to non-existent and / or external data in SQL, without invalidating the file. If SQL is used for exchanging data, any external references must therefore be supplied, or each reference must be replaced by the data referred to.

SQL is a preferred format for file type Databases. Read more about Databases.