Returns nonzero if the specified field in the current record is Null (has no value).
A pointer to the field data member whose status you want to check, or NULL to determine if any of the fields are Null.
Call this member function to determine whether the specified field data member of a recordset has been flagged as Null. (In database terminology, Null means "having no value" and is not the same as NULL in C++.) If a field data member is flagged as Null, it is interpreted as a column of the current record for which there is no value.
This member function is not applicable on recordsets that are using bulk row fetching. If you have implemented bulk row fetching, then IsFieldNull will always return FALSE and will result in a failed assertion. For more information about bulk row fetching, see the article Recordset: Fetching Records in Bulk (ODBC).
IsFieldNull is implemented through DoFieldExchange.