遇到问题。
我定义了一个表来保存每日资金yield curve 的值。
这是一个用于历史查找值的非常简单的表。
表中的年份4、6、8、9、11-19 和21-29 明显存在一些差距。
公式很简单，计算年份4 是0.5*Year3Value + 0.5*Year5Value。
问题是我如何写一个VIEW可以返回丢失的年份？
我可能可以在存储过程中执行此操作，但最终结果需要是一个视图。
【问题讨论】：
标签： sql sql-server sql-view linear-interpolation
Tom H. 假设您真正想要的是线性插值，而且不仅缺少年，而且缺少几个月，您需要将每个计算都基于 MONTH，而不是年。
对于下面的代码，我假设您有 2 个表（其中一个可以作为视图的一部分计算）：
以下代码必须有效（您只需要基于它创建一个视图）：
WITH "Period" (PeriodM, PeriodName) AS (
-- // I would store it as another table basically, but having it as part of the view would do
SELECT 01, '1 mo'
UNION ALL SELECT 02, '2 mo' -- // data not stored
UNION ALL SELECT 03, '3 mo'
UNION ALL SELECT 06, '6 mo'
UNION ALL SELECT 12, '1 yr'
UNION ALL SELECT 24, '2 yr'
UNION ALL SELECT 36, '3 yr'
UNION ALL SELECT 48, '4 yr' -- // data not stored
UNION ALL SELECT 60, '5 yr'
UNION ALL SELECT 72, '6 yr' -- // data not stored
UNION ALL SELECT 84, '7 yr'
UNION ALL SELECT 96, '8 yr' -- // data not stored
UNION ALL SELECT 108, '9 yr' -- // data not stored
UNION ALL SELECT 120, '10 yr'
-- ... // add more
UNION ALL SELECT 240, '20 yr'
-- ... // add more
UNION ALL SELECT 360, '30 yr'
)
, "Yield" (ID, PeriodM, Date, Value) AS (
-- // ** This is the TABLE your data is stored in **
-- //
-- // value of ID column is not important, but it must be unique (you may have your PK)
-- // ... it is used for a Tie-Breaker type of JOIN in the view
-- //
-- // This is just a test data:
SELECT 101, 01 /* '1 mo'*/, '2009-05-01', 0.06
UNION ALL SELECT 102, 03 /* '3 mo'*/, '2009-05-01', 0.16
UNION ALL SELECT 103, 06 /* '6 mo'*/, '2009-05-01', 0.31
UNION ALL SELECT 104, 12 /* '1 yr'*/, '2009-05-01', 0.49
UNION ALL SELECT 105, 24 /* '2 yr'*/, '2009-05-01', 0.92
UNION ALL SELECT 346, 36 /* '3 yr'*/, '2009-05-01', 1.39
UNION ALL SELECT 237, 60 /* '5 yr'*/, '2009-05-01', 2.03
UNION ALL SELECT 238, 84 /* '7 yr'*/, '2009-05-01', 2.72
UNION ALL SELECT 239,120 /*'10 yr'*/, '2009-05-01', 3.21
UNION ALL SELECT 240,240 /*'20 yr'*/, '2009-05-01', 4.14
UNION ALL SELECT 250,360 /*'30 yr'*/, '2009-05-01', 4.09
)
, "ReportingDate" ("Date") AS (
-- // this should be a part of the view (or a separate table)
SELECT DISTINCT Date FROM "Yield"
)
-- // This is the Final VIEW that you want given the data structure as above
SELECT d.Date, p.PeriodName, --//p.PeriodM,
CAST(
COALESCE(y_curr.Value,
( (p.PeriodM - y_prev.PeriodM) * y_prev.Value
+ (y_next.PeriodM - p.PeriodM) * y_next.Value
) / (y_next.PeriodM - y_prev.PeriodM)
) AS DECIMAL(9,4) -- // TODO: cast to your type if not FLOAT
) AS Value
FROM "Period" p
CROSS JOIN "ReportingDate" d
LEFT JOIN "Yield" y_curr
ON y_curr.Date = d.Date
AND y_curr.PeriodM = p.PeriodM
LEFT JOIN "Yield" y_prev
ON y_prev.ID = (SELECT TOP 1 y.ID FROM Yield y WHERE y.Date = d.Date AND y.PeriodM <= p.PeriodM ORDER BY y.PeriodM DESC)
LEFT JOIN "Yield" y_next
ON y_next.ID = (SELECT TOP 1 y.ID FROM Yield y WHERE y.Date = d.Date AND y.PeriodM >= p.PeriodM ORDER BY y.PeriodM ASC)
--//WHERE d.Date = '2009-05-01'
【讨论】：
您可以尝试 unpivot 以获取列表中的年份和值。
然后将它与缺失的年份结合起来 选择年份No , (select YearValue where YearNo = YearNo-1) * 0.5 + (select YearValue where YearNo = YearNo+1) * 0.5 AS YearValue 来自未透视表 其中 YearNo 在（我们缺失的年份列表）
然后再次将其转回以获得您需要的格式并将其弹出到视图中？
【讨论】：
我会猜测，如果存在差距，您希望曲线在两年之间平稳移动，因此如果缺少一年以上，您不想只平均最接近的两年。以下是我可能会使用的：
SELECT
NUM.number AS year,
COALESCE(YC.val, YC_BOT.val + ((NUM.number - YC_BOT.yr) * ((YC_TOP.val - YC_BOT.val)/(YC_TOP.yr - YC_BOT.yr))))
FROM
dbo.Numbers NUM
LEFT OUTER JOIN dbo.Yield_Curve YC ON
YC.yr = NUM.number
LEFT OUTER JOIN dbo.Yield_Curve YC_TOP ON
YC.yr IS NULL AND -- Only join if we couldn't find a current year value
YC_TOP.yr > NUM.number
LEFT OUTER JOIN dbo.Yield_Curve YC_TOP2 ON
YC_TOP2.yr > NUM.number AND
YC_TOP2.yr < YC_TOP.yr
LEFT OUTER JOIN dbo.Yield_Curve YC_BOT ON
YC.yr IS NULL AND -- Only join if we couldn't find a current year value
YC_BOT.yr < NUM.number
LEFT OUTER JOIN dbo.Yield_Curve YC_BOT2 ON
YC_BOT2.yr < NUM.number AND
YC_BOT2.yr > YC_BOT.yr
WHERE
YC_TOP2.yr IS NULL AND
YC_BOT2.yr IS NULL AND
NUM.number BETWEEN @low_yr AND @high_yr
您可以使用 CTE 而不是 Numbers 表（只是一个连续数字表）来重写它。如果你想这样做，你也可以使用 NOT EXISTS 或带有 MIN 和 MAX 的子查询，而不是 YC_BOT2 和 YC_TOP2 上的 LEFT OUTER JOIN。有些人觉得这种方法令人困惑。
【讨论】：
WITh cal(year) AS
(
SELECT 1 AS current_year
UNION ALL
SELECT year + 1
FROM cal
WHERE year < 100
)
SELECT CASE WHEN yield_year IS NULL THEN
0.5 *
(
SELECT TOP 1 yield_value
FROM yield
WHERE yield_year < year
ORDER BY
yield_year DESC
) +
0.5 *
(
SELECT TOP 1 yield_value
FROM yield
WHERE yield_year > year
ORDER BY
yield_year ASC
)
ELSE
yield_value
END
FROM cal
LEFT JOIN
yield
ON yield_year = year
对于缺少的年份，此查询采用找到的最接近年份的平均值。
【讨论】：