将一列添加到下一行mysql中的另一列

Question

我有一个mysql查询如下：

SELECT a.name, ifnull(d.y,0) as y, a.color
                FROM (
                    SELECT 'Jan' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Feb' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Mar' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Apr' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Apr' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'May' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Jun' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Jul' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Aug' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Sep' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Oct' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Nov' name, 0 y, '#6F9BD2' color UNION
                    SELECT 'Dec' name, 0 y, '#6F9BD2' color

                ) AS a LEFT JOIN (
                    SELECT order_date, sum(total_value) AS y
                    FROM saleorder where year(order_date) =".$yearSelect." group by month(order_date)) as d ON a.name = DATE_FORMAT(d.order_date, '%b')

上述查询的结果为

上面提到的mysql查询生成指定年份的所有月份并计算特定月份的总销售额。现在我的问题是，'y'列的值应该通过在以下场景中添加值来计算：

value of y in  jan -> jan
value of y in  feb -> value of y in jan+ value of y in feb
value of y in  march -> value of y in jan+value of y in feb+ value of y in march
.
.
.
december -> jan+feb+march+april+may+jun+jul+aug+sep+oct+nov+december

如何编写mysql查询以获取mysql中此模式的值