Sql 查询以显示每个月的所有项目

我有两个表格：发货（项目，发货数量，发货日期）和预测（项目，发货数量，发货日期），我需要下面的东西

Item   Forecast   Shipped   Forecast_date   Shipped_date
item1  50         100       2018-01-01      2018-01-15
item2  0          50        -               2018-01-06
item3  100        100       2018-02-01      2018-02-05
item4  150        0         2018-02-01      -
item1  0          20        -               2018-03-15
item1  10         50        2018-04-01      2018-04-28

有可能有这样的桌子吗？

---

非常感谢。这看起来相当复杂。您似乎希望在一个月内合并两个表中的行，而不丢失其中任何一个表中的任何值

如果是这样的话，我想这就是你想要的：

select item, max(shipped) as shipped, max(shipped_date) as shipped_date,
       max(forecast) as forecast, max(forecast_date) as forecast_date
from ((select Item, Shipped, Shipped_date, null as forecast, null as forecast_date,
              row_number() over (partition by item, year(shipped_date), month(shipped_date) order by shipped_date) as seqnum
       from shipped
      ) union all
      (select Item, NULL as Shipped, NULL as Shipped_date, null as forecast, null as forecast_date,
              row_number() over (partition by item, year(shipped_date), month(shipped_date) order by shipped_date) as seqnum
       from shipped
      )
     ) sf
group by item, year(coalesce(shipped_date, forecast_date)), 
         month(coalesce(shipped_date, forecast_date)), seqnum

我建议您使用（临时或简单的永久表）

使用外部联接将日历表日期与每个发货日期和预测日期联接。不要忘记将forecast item与shipped item连接起来。如果来自shipped和forecast的数据为空，也要进行处理

SELECT 
    ISNULL(f.item, s.item) AS Item, 
    c.Date, 
    ISNULL(qty_forecat,0) AS Forecast, 
    ISNULL(qty_shipd,0) AS Shipped, 
    date_forecast AS Forecast_date, 
    date_shpd AS Shipped_date
FROM 
    Calendar AS c 
    LEFT OUTER JOIN forecast AS f 
        ON c.Date=f.date_forecast 
    LEFT OUTER JOIN shipped AS s 
        ON c.Date=s.date_shpd 
        AND f.item=s.item

---

您需要显示原始数据。目前还不清楚这些是如何结合起来的。