sql-server - 面额分布计算

Question

一些背景故事:A 公司向挑战的获胜者发放代金券。我目前正在编写的 SQL 需要确定所需的凭证面额，该面额总和为授予某人的值(value)。我有一张表，根据国家和货币存储可用于代金券的面额。

在下面的示例中，特定的人获得了值(value) 80 欧元的代金券。

下面的查询显示了可用于特定国家/地区的凭证面额的查找表的结果。

SELECT * FROM tblDenominationScheme WHERE CountryCode IN ('AT', 'US')

结果:

No. | CountryCode  |   VoucherName | VoucherValue
-------------------------------------------------
1   | AT           |   €50 Shop A  |     50
2   | AT           |   €25 Shop A  |     25
3   | AT           |   €15 Shop A  |     15
4   | AT           |   €10 Shop A  |     10
5   | US           |   $50 Store B |     50
6   | US           |   $10 Store B |     10
7   | US           |   $5 Store B  |      5

我当前的 SQL 如下所示，以确定 80 欧元代金券所需的代金券面额:

   DECLARE @CountryCode1 VARCHAR(2) = 'AT'
   DECLARE @ChallengerID INT = 1172
   DECLARE @RoundedAmount1 INT = 80
   DECLARE @Vouchers INT
   DECLARE @AmountAwarded INT = 0

   SET @AmountAwarded = @RoundedAmount1

   DROP TABLE IF EXISTS #tempVoucher

   CREATE TABLE #tempVoucher
   (
          CountryCode VARCHAR(2),
          ChallengerID INT,
          AmountAwarded INT,
          Vouchers INT,
   )

   WHILE (@RoundedAmount1 > 0)
   BEGIN

          SET @Vouchers = 0

          SELECT TOP 1 @Vouchers = VoucherValue FROM tblDenominationScheme WHERE CountryCode = @CountryCode1 AND VoucherValue <= @RoundedAmount1 ORDER BY VoucherValue DESC

          IF (@Vouchers > 0)
          BEGIN
                 SET @RoundedAmount1 = @RoundedAmount1 - @Vouchers
          END
          ELSE
          BEGIN
                 SELECT TOP 1 @Vouchers = VoucherValue FROM tblDenominationScheme WHERE CountryCode = @CountryCode1 ORDER BY VoucherValue
                 SET @RoundedAmount1 = @RoundedAmount1 - @RoundedAmount1
          END

          INSERT INTO #tempVoucher VALUES (@CountryCode1,@ChallengerID, @AmountAwarded, @Vouchers)
   END

   SELECT * FROM #tempVoucher

上面 SQL 的结果:

No. | CountryCode  | ChallengerID |   AmountAwarded | Vouchers
--------------------------------------------------------------
1   | AT           | 1172         |   80            |   50
2   | AT           | 1172         |   80            |   25
3   | AT           | 1172         |   80            |   10

注意:所有 3 行的 AmountAwarded 列中的值都相同。 3 行的 Vouchers 列中的金额总和应为 80。

上面的结果显然是不正确的，因为如果你将 Vouchers 列中的值相加，它会给你 85，这比 AmountAwarded 多 5

预期结果(或至少最接近):

No. | CountryCode  | ChallengerID |   AmountAwarded | Vouchers
--------------------------------------------------------------
1   | AT           | 1172         |   80            |   50
2   | AT           | 1172         |   80            |   10
3   | AT           | 1172         |   80            |   10
4   | AT           | 1172         |   80            |   10

任何人都可以提供帮助？

Answer 1

这可能是一个昂贵的查询，但为您提供了不同的选择，最多可以提供 7 张优惠券，以获得预期的结果。但是，如果行增加或凭证数量可能更大，这将产生大量读取。

  DECLARE @CountryCode1 VARCHAR(2) = 'AT'
   DECLARE @RoundedAmount1 INT = 80;

WITH cteDenominations AS(
    SELECT No, VoucherValue 
    FROM tblDenominationScheme 
    WHERE CountryCode = @CountryCode1
    UNION ALL
    SELECT 10000, 0
),
ctePermutations AS(
    SELECT a.No             AS a_No, 
           a.VoucherValue   AS a_Value, 
           b.No             AS b_No, 
           b.VoucherValue   AS b_Value,
           c.No             AS c_No, 
           c.VoucherValue   AS c_Value,
           d.No             AS d_No, 
           d.VoucherValue   AS d_Value,
           e.No             AS e_No, 
           e.VoucherValue   AS e_Value,
           f.No             AS f_No, 
           f.VoucherValue   AS f_Value,
           g.No             AS g_No, 
           g.VoucherValue   AS g_Value,
        ROW_NUMBER() OVER(ORDER BY a.No, b.No, c.No, d.No) Permutation
    FROM cteDenominations a
    JOIN cteDenominations b ON a.VoucherValue >= b.VoucherValue
    JOIN cteDenominations c ON b.VoucherValue >= c.VoucherValue
    JOIN cteDenominations d ON c.VoucherValue >= d.VoucherValue
    JOIN cteDenominations e ON d.VoucherValue >= e.VoucherValue
    JOIN cteDenominations f ON e.VoucherValue >= f.VoucherValue
    JOIN cteDenominations g ON f.VoucherValue >= g.VoucherValue
    WHERE @RoundedAmount1 = a.VoucherValue 
                          + b.VoucherValue 
                          + c.VoucherValue 
                          + d.VoucherValue 
                          + e.VoucherValue 
                          + f.VoucherValue 
                          + g.VoucherValue 
)
SELECT Permutation,
    u.No,
    u.VoucherValue
FROM ctePermutations
CROSS APPLY (VALUES(a_No, a_Value),
                   (b_No, b_Value),
                   (c_No, c_Value),
                   (d_No, d_Value),
                   (e_No, e_Value),
                   (f_No, f_Value),
                   (g_No, g_Value))u(No, VoucherValue)
WHERE VoucherValue > 0
AND   Permutation = 1 --Remove this to get all possibilities
;