Sql 在计算年初至今时填写缺失的月份

我今天有一张桌子

year month qty_ytd
2017   01    20
2017   02   30
2018   01    50

我需要填写gabs在同一年中缺失的月份，直到12月：

结果举例如下：

year month qty_ytd
2017   01    20
2017   02   30
2017   03   30
.....
2017   07   30
2017   12   30

2018   01    50
2018   02    50
....
2018   12    50

怎么做？我没有弄清楚如何填充缺少的月份？

您可以使用交叉连接生成行并交叉应用以获取数据：

select y.y, v.m, t.qty_ytd
from (select distinct year from t) y cross join
     (values (1), (2), (3), (4), . . . (12)) v(m) outer apply
     (select top (1) t.*
      from t
      where t.year = y.year and
            t.month <= y.m
      order by t.m desc
     ) t;

---

另一个选项是计算增量，添加虚拟零增量，恢复运行总计。我更改了源数据以显示更常见的情况

create table #t
(
 year int,
 month int, 
 qty_ytd int
);

insert #t(year, month, qty_ytd )
values
(2017,   01,   20),
(2017,   02,   30),
(2018,   04,   50) -- note month
;

select distinct year, month, sum(delta) over(partition by year order by  month)
from (
    -- real delta
    select year, month, delta = qty_ytd - isnull(lag(qty_ytd) over (partition by year order by month),0)
    from #t
    union all
    -- tally dummy delta
    select top(24) 2017 + (n-1)/12, n%12 + 1 , 0
    from 
    ( select row_number() over(order by a.n) n
      from
      (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) a(n),
      (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) b(n)
    ) c
)d
order by year, month;

---

你的问题是什么？你已经说了你想要什么，但什么都没问。你试过什么？关于如何做到这一点，有很多例子。就我个人而言，我推荐一个理货表或日历表。在您编写的第一个查询中，我需要从select distinct year中添加m，从t y交叉连接中添加m，对吗？@csharp。不，那是一种类型。应该是，现在是v.m。在第一个查询中，我需要更改其中t.year=y.year和t.m

create table #t
(
 year int,
 month int, 
 qty_ytd int
);

insert #t(year, month, qty_ytd )
values
(2017,   01,   20),
(2017,   02,   30),
(2018,   04,   50) -- note month
;

select distinct year, month, sum(delta) over(partition by year order by  month)
from (
    -- real delta
    select year, month, delta = qty_ytd - isnull(lag(qty_ytd) over (partition by year order by month),0)
    from #t
    union all
    -- tally dummy delta
    select top(24) 2017 + (n-1)/12, n%12 + 1 , 0
    from 
    ( select row_number() over(order by a.n) n
      from
      (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) a(n),
      (values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10)) b(n)
    ) c
)d
order by year, month;