SQL查询，外连接，cte？需要使用“左”值修复运行总计

Question

我几天来一直在尝试纠正这个查询。基本上在每个acount_no 和group 的一组中，只需要扣除小于最大组的金额。

基本上，账户 104 的 maxgroup 为 99，第一个金额是 75，因为 take 将是 75，left 将是 24，那么对于下一个 B 组，即使需要的数量是 64，因为只剩下 24，所以 B 组将只得到 24，之后什么都没有，所以 D 组将剩下 0。

基本上我的表可以有这样的值

DECLARE @table AS TABLE(acc_no INT, [group] CHAR(1), [maxgroup] INT, amount INT)

INSERT INTO @table VALUES
(101, 'A', 70, 0),
(101, 'B', 70, 50),
(101, 'C', 70, 0),
(101, 'D', 70, 20),
(102, 'A', 95, 30),
(102, 'B', 95, 0),
(102, 'C', 95, 5),
(102, 'D', 95, 10),
(103, 'A', 80, 40),
(103, 'B', 80,15),
(103, 'C', 80, 10),
(103, 'D', 80, 5),
(104, 'A', 99.53, 75),
(104, 'B', 99.53,64),
(104, 'D', 99.53, 0.53),

(105, 'A', 21.5, 75),
(105, 'D', 21.5,6)



SELECT t.acc_no, 
    t.[group],
    t.maxgroup,t.amount,
    CASE WHEN t1.assigned = 0 THEN NULL ELSE t.amount END AS taken, 
    CASE WHEN t1.assigned = 0 THEN NULL ELSE (t.maxgroup - t1.assigned) END [left]
FROM @table t
OUTER APPLY(SELECT SUM([amount]) AS assigned 
            FROM @table t1 WHERE t1.acc_no = t.acc_no AND t1.[group] <= t.[group]) t1

这是我期望的结果：

 acc_no group   maxgroup    amount  taken   left
101 A   70      0   NULL    NULL
101 B   70      50  50  20
101 C   70      0   0   20
101 D   70      20  20  0
102 A   95      30  30  65
102 B   95      0   0   65
102 C   95      5   5   60
102 D   95      10  10  50
103 A   80      40  40  40
103 B   80      15  15  25
103 C   80      10  10  15
103 D   80      5   5   10
104 A   99      75  75  24
104 B   99      64  24  0    --<<
104 D   99      0   0   0
105 A   21      75  21  0
105 D   21      6   0   0

不幸的是，我的查询为acc_no=104 的left 列提供了负值。

Answer 1

你们很亲密：

CASE 
  WHEN t1.assigned = 0 THEN NULL 
  WHEN t.maxgroup < t1.assigned THEN 0 --<< that's it
  ELSE (t.maxgroup - t1.assigned) 
END [left]

但我的建议是：

SELECT t.acc_no, 
    t.[group],
    t.maxgroup,
    t.amount,
    CASE 
      WHEN t.amount = 0 THEN 0
      WHEN t.maxgroup < (t.running_total-t.amount) THEN 0
      WHEN t.maxgroup < t.running_total THEN t.amount - (t.running_total - t.maxgroup)
      ELSE t.amount
    END taken,
    CASE 
      WHEN t.maxgroup < t.running_total THEN 0
      ELSE t.maxgroup - t.running_total
    END [left]
FROM (
  SELECT t.acc_no, 
      t.[group],
      t.maxgroup,
      t.amount,
      SUM(t.amount) OVER(PARTITION BY t.[acc_no] ORDER BY t.[group] ROWS UNBOUNDED PRECEDING) running_total
  FROM stock t
) t
order by 1, 2

这一项只会对源表进行一次扫描。而不是使用子查询方法的许多循环。

http://sqlfiddle.com/#!18/ce2f5/12

Answer 2

为了保持查询逻辑，您可以跟踪每个组的前一行总数，如下所示：

SELECT t.acc_no, 
    t.[group],
    t.maxgroup, t.amount, 
    CASE WHEN A.previous_assigned + t.amount <= t.maxgroup THEN t.amount
    ELSE CASE When (t.maxgroup - A.previous_assigned) > 0 Then (t.maxgroup - A.previous_assigned)
        ELSE 0
        END 
    END AS taken, 
    CASE WHEN  (t.maxgroup - A.previous_assigned - t.amount) <= 0 THEN 0 
    ELSE (t.maxgroup - A.previous_assigned - t.amount) 
    END AS [left]
FROM @table t
OUTER APPLY(SELECT SUM([amount]) AS assigned, (SUM([amount]) - t.amount) AS previous_assigned
            FROM @table t1 WHERE t1.acc_no = t.acc_no AND t1.[group] <= t.[group]) As A;