Question

我正在尝试提取一个非常简单的报告，以查看前一天的数据。看起来类似于：

SELECT Name, Date, Count
FROM dbo.X
WHERE Date BETWEEN DATEADD(DD, -1, GETDATE()) AND DATEADD(DD, 0, GETDATE())

这很好，但是我被要求提供一列以显示前一天的数量，以供比较。我不确定如何执行此操作，因为datetime条件已经指定了最后一天。有没有一种方法可以使这项工作使选择列表看起来像这样？

SELECT Name, Date, YesterdaysCount, Count

编辑：示例数据：

Name    Date    Count
a   6/22/2020   1
b   6/22/2020   2
c   6/22/2020   3
d   6/22/2020   4
e   6/22/2020   5
a   6/21/2020   2
b   6/21/2020   4
c   6/21/2020   6
d   6/21/2020   8
e   6/21/2020   10

所需结果：

Name    Date    YesterdayCount  Count
a   6/22/2020   2   1
b   6/22/2020   4   2
c   6/22/2020   6   3
d   6/22/2020   8   4
e   6/22/2020   10  5

Answer 1

如果您没有时间组件，这应该可以工作。如果这样做的话，只需将“ Y. [Date] =”更改为与第一部分相同的内容即可。

SELECT [Name], [Date], [Count], 
   (SELECT SUM(Y.[Count]) FROM dbo.X AS Y WHERE Y.[Name] = X.[Name] AND Y.[Date] = DATEADD(DAY, -1, X.[DATE]) AS YesterdaysCount
FROM dbo.X
WHERE [Date] BETWEEN DATEADD(DD,-1,GETDATE()) AND DATEADD(DD, 0, GETDATE())

Answer 2

有很多方法可以做到这一点，这是两种方法。我建议每天使用变量如果您只关心日期，我建议您使用日期而不是日期时间，这样可以加快搜索速度（包括变量和投射日期字段）

declare @table1 table (name varchar(10), YourDate datetime, YourCount int ) 

insert into @table1 values ('name1', '2020-06-19', 1)
--insert into @table1 values ('name1', '2020-06-20', 1)
insert into @table1 values ('name1', '2020-06-21', 2)
insert into @table1 values ('name1', '2020-06-22', 3)
insert into @table1 values ('name1', '2020-06-23', 4)
insert into @table1 values ('name1', '2020-06-24', 5)

--use date fiels for faster comparisson
declare @Today date=getdate(), @Yesterday date=dateadd(day,-1,getdate())

--using a left join to the same table for yesterdays (check for nulls)
SELECT t1.Name, t1.YourDate, 
    sum(isnull(t2.YourCount,0)) as YesterdayCount,
    sum(isnull(t1.YourCount,0)) as TodayCount
From @table1 t1
Left Join @table1 t2  on t1.name=t2.name and t2.YourDate=cast(dateadd(day,-1,t1.YourDate) as date)
Where cast(t1.YourDate as date) BETWEEN @Yesterday AND @Today
Group By t1.name, t1.YourDate

--using outer apply
SELECT t1.Name, t1.YourDate, 
    sum(isnull(t2.YourCount,0)) as YesterdayCount,
    sum(isnull(t1.YourCount,0)) as TodayCount
From @table1 t1
outer apply(
    Select t3.YourCount From @table1 t3 where t3.YourDate=cast(dateadd(day,-1,t1.YourDate) as date)
) as t2
Where cast(t1.YourDate as date) BETWEEN @Yesterday AND @Today
Group By t1.name, t1.YourDate

Answer 3

SELECT 
    Name, Date,
    (SELECT Count 
     WHERE Date BETWEEN DATEADD(DD, -2, GETDATE()) AND DATEADD(DD, -1, GETDATE())) AS YesterdaysCount, Count
FROM
    dbo.X
WHERE
    Date BETWEEN DATEADD(DD, -1, GETDATE()) AND DATEADD(DD, 0, GETDATE())

有没有一种方法可以让SQL SELECT具有不同日期的列？

3 个答案: