MDAC 2.5 SDK - ODBC Programmer's Reference
Appendix G: Driver Guidelines for Backward Compatibility

SQLColAttributes Mapping

When an application calls SQLColAttributes through an ODBC 3.x driver, the call to SQLColAttributes is mapped to SQLColAttribute as follows:

Note   The prefix used in FieldIdentifier values in ODBC 3.x has been changed from that used in ODBC 2.x. The new prefix is "SQL_DESC"; the old prefix was "SQL_COLUMN".

1. If the application is an ODBC 2.x application, fDescType is SQL_COLUMN_TYPE, and the returned type is a concise DATETIME type, the Driver Manager maps the return values for date, time, and timestamp codes.
   
   
2. If fDescType is SQL_COLUMN_NAME, SQL_COLUMN_NULLABLE, or SQL_COLUMN_COUNT, the Driver Manager calls SQLColAttribute in the driver with the FieldIdentifier argument mapped to SQL_DESC_NAME, SQL_DESC_NULLABLE, or SQL_DESC_COUNT, as appropriate. All other values of fDescType are passed through to the driver.

An ODBC 3.x driver must support all the ODBC 3.x FieldIdentifiers listed for SQLColAttribute.

An ODBC 3.x driver must support SQL_COLUMN_PRECISION and SQL_DESC_PRECISION, SQL_COLUMN_SCALE and SQL_DESC_SCALE, and SQL_COLUMN_LENGTH and SQL_DESC_LENGTH. These values are different because precision, scale, and length are defined differently in ODBC 3.x than they were in ODBC 2.x. For more information, see "Column Size, Decimal Digits, Transfer Octet Length, and Display Size" in Appendix D, "Data Types."