Question

我有三张表ElecUser，ElecUsage，ElecEmissionFactor
ElecUser: UserID UserName 1 Main Building 2 Staff Quarter

ElecUsage: UserID Time Amount 1 1/7/2010 23230 1 8/10/2011 34340 1 8/1/2011 34300 1 2/3/2012 43430 1 4/2/2013 43560 1 3/2/2014 44540 2 3/6/2014 44000

ElecEmissionFactor: Time CO2Emission 1/1/2010 0.5 1/1/2011 0.55 1/1/2012 0.56 1/1/2013 0.57

预期结果：
UserName Time CO2 1 2010 11615 1 2011 37752 (34340*0.55 + 34300*0.55) 1 2012 24320.8 1 2013 24829.2 1 2014 25387.8 2 2014 25080

逻辑是ElecUsage.Amount * ElecEmissionFactor。如果是同一用户和同一年，请将它们添加到该年的记录中。我的疑问是：
SELECT ElecUser.UserName, Year([ElecUsage].[Time]), SUM((ElecEmissionFactor.CO2Emission*ElecUsage.Amount)) As CO2 FROM ElecEmissionFactor, ElecUser INNER JOIN ElecUsage ON ElecUser.UserID = ElecUsage.UserID WHERE (((Year([ElecUsage].[Time]))>=Year([ElecEmissionFactor].[Time]))) GROUP BY ElecUser.UserName, Year([ElecUsage].[Time]) HAVING Year([ElecUsage].[Time]) = Max(Year(ElecEmissionFactor.Time));

然而，这仅显示具有排放因子的年份面临的挑战是将没有排放因子的年份引入最近一年的排放因子子查询可能是解决方案之一，但我没有这样做我被困了一会儿。希望看到你的回复感谢

Answer 1

尝试这样的事情......

- 未经测试

select T1.id, year(T1.time) as Time, sum(T1.amount*T2.co2emission) as CO2 
from ElecUsage T1 
left outer join ElecEmissionFactor T2 on (year(T1.time) = year(T2.time))
Group by year(T1.time), T1.id

使用子查询以这种方式获取相应的因子

    select T1.id, 
        year(T1.time) as Time, 
        sum(T1.amount*
                    (
                    select top 1 CO2Emission from ElecEmissionFactor T2 
                    where year(T2.time) <= year(T1.time) order by T2.time desc
                    )
        ) as CO2 
from ElecUsage T1 
Group by year(T1.time), T1.id

交叉参考最近的日期数据

1 个答案: