def add_column(self, tablename: str, fieldspec: FIELDSPEC_TYPE) -> int:
        """Adds a column to an existing table."""
        sql = "ALTER TABLE {} ADD COLUMN {}".format(
            tablename, self.fielddefsql_from_fieldspec(fieldspec))
        log.info(sql)
        return self.db_exec_literal(sql)
Adds a column to an existing table.