The SQL_DESC_TD_UDT_NAME descriptor record field contains the Fully Qualified Type Name of the UDT column.
When extended statement information is not available, the value of the SQL_DESC_TD_UDT_NAME descriptor field will always be empty string.
With extended statement information available, the value of the SQL_DESC_TD_UDT_NAME descriptor field will have Fully Qualified Type Name based on the column definition.