MDAC 2.5 SDK - ODBC Programmer's Reference
Appendix C: SQL Grammar

Data Type Support

ODBC drivers must support at least one of SQL_CHAR and SQL_VARCHAR. Support for other data types is determined by the driver's or data source's SQL-92 conformance level. An application should call SQLGetTypeInfo to determine the data types supported by the driver.

For more information on data types, see Appendix D, "Data Types."