计算多个订单的核销金额

CREATE TABLE #t 
( id INT ,
dingdan VARCHAR(20),
sale MONEY
) 

INSERT INTO  #t VALUES (1,‘a‘,100);
INSERT INTO  #t VALUES (2,‘b‘,200);    
INSERT INTO  #t VALUES (3,‘c‘,300);    
INSERT INTO  #t VALUES (4,‘d‘,400);    
INSERT INTO  #t VALUES (5,‘e‘,500);    
INSERT INTO  #t VALUES (6,‘f‘,600);    
INSERT INTO  #t VALUES (7,‘g‘,700);
INSERT INTO  #t VALUES (8,‘h‘,800);
INSERT INTO  #t VALUES (9,‘i‘,900);
INSERT INTO  #t VALUES (10,‘j‘,1000);

;WITH    x1
          AS ( SELECT   t1.id ,
                        t1.dingdan ,
                        t1.sale ,
                        ( SELECT    ISNULL(SUM(t2.sale), 0)
                          FROM      #t t2
                          WHERE     t2.id < t1.id
                        ) AS curr_sale_sum--本订单之前的所有订单金额
               FROM     #t t1
             ),/*计算出核销金额*/
        x2
          AS ( SELECT   id ,
                        dingdan ,
                        sale ,
                        CASE WHEN curr_sale_sum + sale <= 1700 THEN sale
                             ELSE 1700 - curr_sale_sum
                        END AS new_sale
               FROM     x1
             )
     /*核销金额为负数，则变更为0*/
    SELECT  id AS 序号,
            dingdan 订单,
            sale 订单金额,
            CASE WHEN new_sale < 0 THEN 0
                 ELSE new_sale
            END AS 核销金额
    FROM    x2