def cast_temp_col(db, type_, col, errors_table=None):

    '''Like cast(), but creates a new column with the cast values if the input

    is a column.

    @return The new column or cast value

    '''

    def cast_(col): return cast(db, type_, col, errors_table)

    try: col = sql_gen.underlying_col(col)

    except sql_gen.NoUnderlyingTableException: return sql_gen.wrap(cast_, col)

    table = col.table

    new_col = sql_gen.Col(sql_gen.concat(col.name, '::'+type_), table, col.srcs)

    expr = cast_(col)

    add_col(db, table, sql_gen.TypedCol(new_col.name, type_))

    update(db, table, [(new_col, expr)])

    return new_col