def get_schema_name(full_qualified_table_name):
    """Extracts the schema name from a full qualified table name.

    Parameters
    ----------
    full_qualified_table_name : str, mandatory
        A full qualified table name (i.e. schema name and table name)

    Returns
    -------
    The schema name or None.
    """
    pos = full_qualified_table_name.rfind('.')
    if pos == -1:
        return None
    name = full_qualified_table_name[0:pos]
    return name
