MDAC 2.5 SDK - ODBC Programmer's Reference
Appendix F: ODBC Cursor Library
The cursor library executes SQLSetDescField when it is called to return the value of the fields set for bookmark columns: SQL_DESC_DATA_PTR, SQL_DESC_INDICATOR_PTR, SQL_DESC_OCTET_LENGTH_PTR, SQL_DESC_LENGTH, SQL_DESC_OCTET_LENGTH, SQL_DESC_DATETIME_INTERVAL_CODE, SQL_DESC_SCALE, SQL_DESC_PRECISION, SQL_DESC_TYPE, SQL_DESC_NAME, SQL_DESC_UNNAMED, and SQL_DESC_NULLABLE. The cursor library executes calls to SQLSetDescRec for a bookmark column.
When working with an ODBC 2.x driver, the cursor library returns SQLSTATE HY090 (Invalid string or buffer length) when SQLSetDescField or SQLSetDescRec is called to set the SQL_DESC_OCTET_LENGTH field for the bookmark record of an ARD to a value not equal to 4. When working with an ODBC 3.x driver, the cursor library allows the buffer to be any size.
The cursor library executes SQLSetDescField when it is called to return the value of the SQL_DESC_BIND_OFFSET_PTR, SQL_DESC_BIND_TYPE, SQL_DESC_ROW_ARRAY_SIZE, or SQL_DESC_ROW_STATUS_PTR field. These fields can be returned for any row, not just the bookmark row.
The cursor library does not execute SQLSetDescField to change any descriptor field other than the fields mentioned previously. If an application calls SQLSetDescField to set any other field while the cursor library is loaded, the call is passed through to the driver.
The cursor library supports changing the SQL_DESC_DATA_PTR, SQL_DESC_INDICATOR_PTR, and SQL_DESC_OCTET_LENGTH_PTR fields of any row of an application row descriptor dynamically (after a call to SQLExtendedFetch, SQLFetch, or SQLFetchScroll). The SQL_DESC_OCTET_LENGTH_PTR field can be changed to a null pointer only to unbind the length buffer for a column.
The cursor library does not support changing the SQL_DESC_BIND_TYPE field in an APD or ARD when a cursor is open. The SQL_DESC_BIND_TYPE field can be changed only after the cursor is closed and before a new cursor is opened. The only descriptor fields that the cursor library supports changing when a cursor is open are SQL_DESC_ARRAY_STATUS_PTR, SQL_DESC_BIND_OFFSET_PTR, SQL_DESC_DATA_PTR, SQL_DESC_INDICATOR_PTR, SQL_DESC_OCTET_LENGTH_PTR, and SQL_DESC_ROWS_PROCESSED_PTR.
The cursor library does not support modifying the SQL_DESC_COUNT field of the ARD after SQLExtendedFetch or SQLFetchScroll has been called and before the cursor has been closed.