Sql server 2008 如何计算和YTD格式

我有表格付款（实际有大约10万条记录、不同类别、客户等）：

我想对每个客户的分类税进行累计累计。所以结果是这样的：

Client      Dt          Amt  Category
  1       201312        10       Tax
  1       201401        10       Tax
  1       201405        20       Tax
  1       201406        30       Tax
  2       201311        10       Tax

谢谢

试试这个：

SELECT a.Client, a.Dt, SUM(b.Amt) AS Amt, a.Category
FROM payments a
JOIN payments b ON b.Client = a.Client
 AND b.Category = a.Category
 AND b.Dt <= a.Dt
 AND YEAR(b.Dt) = YEAR(a.Dt)
WHERE a.Category = 'Tax'
GROUP BY a.Client, a.Dt, a.Category

选择a.客户、a.Dt、金额（b.金额）作为金额，a.类别
从a付款
在b.Client=a.Client上加入付款b
b类=a类
和b.Dt
SELECT a.Client, a.Dt, SUM(b.Amt) AS Amt, a.Category
FROM payments a
JOIN payments b ON b.Client = a.Client
 AND b.Category = a.Category
 AND b.Dt <= a.Dt
 AND YEAR(b.Dt) = YEAR(a.Dt)
WHERE a.Category = 'Tax'
GROUP BY a.Client, a.Dt, a.Category