SQL填写缺少日期

Question

我有我猜测的是一个常见的数据仓库问题。

我一直在试图做的是做一个SQL日期之间没有差距的查询。

事实表只记录被测量并记录到表中的记录。这个案例涉及海上船只的注册石油生产。有些日子有些船上没有生产。

所以这里是我的简单数据仓库：DimVessel,DimDate和FactProduction。在下面你看到我想要的最终结果集。

我希望SQL Query能够用vesselkey和Production填充事实表，即使船上没有生产。请记住，有些日子可能会在少数船舶上生产，其他日子可能会生产所有船舶（最好的情况）。

我希望有人能帮助我。

DimVessel

VesselKey| VesselName 
1  | Vessel 1 
2  | Vessel 2 
3  | Vessel 3 
4  | Vessel 4 
5  | Vessel 5 

DimDate

DateKey  |Date 
20160517 |2016-05-17 00:00:00.000 
20160518 |2016-05-18 00:00:00.000 
20160519 |2016-05-19 00:00:00.000 
20160520 |2016-05-20 00:00:00.000 

FactProduction

DateKey  |VesselKey |Production 
20160517 |4   |12505 
20160517 |5   |1276 
20160517 |3   |88 
20160517 |2   |3919 
20160518 |4   |8785 
20160518 |5   |736 
20160518 |1   |3754 
20160518 |2   |5654 
20160519 |2   |1654 
20160520 |1   |2016 
20160520 |3   |6059 
20160520 |4   |10980 
20160520 |5   |663 

这是我はnt，最终结果集：

DateKey  |VesselKey |Production 
20160517 |4   |12505 
20160517 |5   |1276 
20160517 |3   |88 
20160517 |2   |3919 
20160517 |1   |0 
20160518 |4   |8785 
20160518 |5   |736 
20160518 |3   |0 
20160518 |1   |3754 
20160518 |2   |5654 
20160519 |2   |1654 
20160519 |1   |0 
20160519 |3   |0 
20160519 |4   |0 
20160519 |5   |0 
20160520 |1   |2016 
20160520 |3   |6059 
20160520 |2   |4059 
20160520 |4   |10980 
20160520 |5   |663 

Answer 1

为什么要存储不存在的数据？我不喜欢存储实际上不存在于源系统中的事实数据。

你可以达到你想要用下面的查询（未测试）

SELECT DD.DateKey 
,DV.VesselKey 
,Production = ISNULL(FP.Production) 
FROM DimDate DD 
    INNER JOIN DimVessel DV ON 1 = 1 
    LEFT JOIN FactProduction FP ON (FP.DateKey = DD.DateKey AND FP.VesselKey = DV.VesselKey) 
WHERE DD.DateKey BETWEEN @StartDate AND @EndDate 

如果你坚持想保存数据，那么你只需要添加一个连接到您的源数据，而不是结果FactProduction表，然后将结果插入到你的事实

Answer 2

这里是一个有效的解决方案：

select allCombinations.DateKey, 
     allCombinations.VesselKey, 
     isnull(p.Production, 0) as Production 
from (
     select d.DateKey, 
       v.VesselKey 
     from @Dates as d 
     cross join @Vessels as v 
     ) as allCombinations 
left join @Production as p 
on  allCombinations.DateKey = p.DateKey 
     and allCombinations.VesselKey = p.VesselKey 

为了验证该解决方案的完整的代码是后续ing：

declare @Vessels table 
    (
    VesselKey int primary key 
        not null, 
    VesselName as (N'Vessel ' + cast(VesselKey as nvarchar)) 
    ) 

insert into @Vessels 
     (VesselKey) 
values (1), 
     (2), 
     (3), 
     (4), 
     (5) 

select * 
from @Vessels as v 

declare @Dates table 
    (
    DateKey int primary key 
       not null, 
    Date as (try_convert(datetime2, cast(DateKey as nvarchar) 
       + ' 00:00:00.000')) 
    ) 

insert into @Dates 
     (DateKey) 
values (20160517), 
     (20160518), 
     (20160519), 
     (20160520) 

select * 
from @Dates as d 

declare @Production table 
    (
    DateKey int, 
    VesselKey int, 
    Production int 
    ) 

insert into @Production 
     (DateKey, VesselKey, Production) 
values (20160517, 4, 12505), 
     (20160517, 5, 1276), 
     (20160517, 3, 88), 
     (20160517, 2, 3919), 
     (20160518, 4, 8785), 
     (20160518, 5, 736), 
     (20160518, 1, 3754), 
     (20160518, 2, 5654), 
     (20160519, 2, 1654), 
     (20160520, 1, 2016), 
     (20160520, 3, 6059), 
     (20160520, 4, 10980), 
     (20160520, 5, 663) 

select * 
from @Production as p 



select allCombinations.DateKey, 
     allCombinations.VesselKey, 
     isnull(p.Production, 0) as Production 
from (
     select d.DateKey, 
       v.VesselKey 
     from @Dates as d 
     cross join @Vessels as v 
     ) as allCombinations 
left join @Production as p 
on  allCombinations.DateKey = p.DateKey 
     and allCombinations.VesselKey = p.VesselKey 

让我知道如果结果不是你要找的那个。