计算缺失的月份

Question

我使用以下查询来填补缺失的月份

Declare @Sample Table(year int, month int,product as nvarchar(50), qty_ytd int);
Insert @Sample(year, month, qty_ytd) Values
(2017,   01,'book',    20),
(2017,   02, 'pc',   30),
(2018,   01, 'book',    50);

;With Months As
(Select 1 As month
Union All
Select month + 1 From Months Where month < 12)
, YearsAndMonths As
(Select distinct year,m.month from @Sample cross join Months m)

select ym.*, coalesce(s.qty_ytd, s2.qty_ytd) qty_ytd, coalesce(s.qty_ytd, 0) QTY from YearsAndMonths ym
left join @sample s on ym.year = s.year and ym.month = s.month
left join (select qty_ytd, year,
                  row_number() over (partition by year order by month desc) rn
           from @Sample) s2 on ym.year = s2.year and rn = 1

我怎样才能添加“产品”？

Answer 1

首先，我建议创建一个日历表，因为它每隔一段时间就会作为一个用例弹出。一个简单的例子可以找到here

现在，一旦您准备好日历表（我们称之为 static.calendar），代码就相当简单，如下所示：

with Products
as
(
    SELECT distinct product
    FROM @Sample
),
TimeRange
as
(
    SELECT DISTINCT year,
        month
    FROM static.calendar
)
ProductTimeRange
as
(
    SELECT p.products,
        tr.year,
        tr.month
    FROM Products as p
    CROSS JOIN TimeRange as tr
)
SELECT ptr.products,
    ptr.year,
    ptr.month,
    s.qty_ytd
FROM ProductTimeRange as ptr
LEFT JOIN @sample as s
    ON ptr.products = s.products
    AND ptr.year = s.year
    AND ptr.month = s.month
ORDER BY ptr.products,
    ptr.year,
    ptr.month

---

Answer 2

使用cross join 生成您想要的行——所有年份、月份和产品。

然后使用left join 带入你想要的数据：

With Months As (
      Select 1 As month
      Union All
      Select month + 1
      From Months
      Where month < 12
     )
select y.year, m.month, s.product, coalesce(qty_ytd, 0) as qty_ytd
from (select distinct year from @sample) y cross join
     months m cross join
     (select distinct product from @sample) p left join
     @sample s
     on s.year = y.year and s.month = m.month and s.product = p.product;

Here 是一个 dbfiddle。