Driver conformance levels

When the ANSI group created the SQL-92 standard, they defined three distinct levels of SQL functionality: Entry, Intermediate, and Full. The ODBC standard goes one step further by defining conformance levels for drivers in two areas; the ODBC API and the ODBC SQL grammar.

Conformance levels were incorporated into ODBC for the following reasons:

• To provide a way for applications and drivers to implement portions of the ODBC API, specific to their needs, without having to implement complete functionality. This allows simpler, smaller drivers to be developed for implementations that do not need full functionality.

• To align ODBC with current CLI standards so that the distinction between truly standard and extension portions of the ODBC API would be immediately apparent.

• To help achieve interoperability at lower conformance levels, an application has less work to do to operate with multiple data sources. The drawback is that the lower conformance levels provide less functionality. Higher conformance levels provide an application with greater power. However, programming for higher conformance levels requires an application to be more complex.

Conformance levels facilitate programming applications by defining a standard set of functionality that both the driver developer and application developer can rely on. By definition, if a driver claims to conform to a specific API or SQL conformance level, it must support all of the functionality defined by that conformance level. If the data source associated with a driver does not provide some of the functionality defined for a conformance level, the driver must either provide the missing functionality itself or claim to conform to a lower conformance level. The application discovers a driver’s interface conformance level by connecting to a data source, and calling SQLGetInfo with the SQL_ODBC_INTERFACE_CONFORMANCE option. Drivers are free to implement features beyond the level to which they claim complete conformance. Applications discover any such additional capabilities by calling SQLGetFunctions (to determine which ODBC functions are present) and SQLGetInfo (to query various other ODBC capabilities).