SQL Server 用最后一个值替换 NULL [重复]

我想找到一种方法用最后一个非 NULL 值替换 NULL 值。 我有一张像这样的桌子：

Date        Cost
2017-01-01  18.6046511
2017-01-03  22.9787234
2017-01-03  NULL
2017-01-12  18.8584937
2017-01-16  19.1827852
2017-01-16  NULL
2017-01-19  NULL
2017-02-21  NULL
2017-03-04  24.0597622
2017-03-28  NULL
2017-04-17  33.5398414
2017-04-17  NULL

我想用最后一个非 NULL 值替换 NULL 值 所以结果会是这样的：

Date        Cost
2017-01-01  18.6046511
2017-01-03  22.9787234
2017-01-03  22.9787234
2017-01-12  18.8584937
2017-01-16  19.1827852
2017-01-16  19.1827852
2017-01-19  19.1827852
2017-02-21  19.1827852
2017-03-04  24.0597622
2017-03-28  24.0597622
2017-04-17  33.5398414
2017-04-17  33.5398414

您可以通过创建使用窗框组 (GUWF) 来尝试以下查询。来源链接 https://www.red-gate.com/simple-talk/sql/t-sql-programming/filling-in-missing-values-using-the-t-sql-window-frame/.

create table MyTable ([dtDate] date, Cost decimal(18, 6))
insert into MyTable values 
('2017-01-01',  18.6046511),
('2017-01-03',  22.9787234),
('2017-01-03',  NULL),
('2017-01-12',  18.8584937),
('2017-01-16',  19.1827852),
('2017-01-16',  NULL),
('2017-01-19',  NULL),
('2017-02-21',  NULL),
('2017-03-04',  24.0597622),
('2017-03-28',  NULL),
('2017-04-17',  33.5398414),
('2017-04-17',  NULL)

SELECT dtDate, Cost = MAX(Cost) OVER (PARTITION BY c)
FROM
(
    SELECT dtDate, Cost
        ,c = count(Cost) OVER (ORDER BY dtDate)
    FROM MyTable
) a
ORDER BY dtDate;