Sql server 获取SQL Server中两列的%差异

我正在根据给定的月份/年份为列选择计数。我需要返回与上个月相比的百分比差异

这是我到目前为止所做的。这将返回我需要的前半部分（当前月份计数）

因此，它的输出如下所示

Widget 1  - 200 sold
Widget 2  - 190 sold

同样，我还想包括第三列，它捕获了上个月的%变化

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另外，对于如何使用

datePart

进行选择，我也不是很清楚，因此如果您对如何更好地进行选择有什么建议，我将不胜感激

有很多方法可以产生你想要的结果。这一个使用一个CTE来计算两个月的总数，然后将其合并回自身

With cte as 
(
SELECT 

       o.productname, 
       Datepart(month, datetimereceived) m,
       Count(*) AS totalSales 
FROM   order o 
       INNER JOIN product p 
               ON o.productid = p.productid 
WHERE  Datepart(month, datetimereceived) in ( 2, 2-1) 
       AND Datepart(year, datetimereceived) = 2012 
GROUP  BY o.productname, 
       Datepart(month, datetimereceived) 
ORDER  BY totalsales DESC )
SELECT 
      a.productName ,
      a.totalSales,
      a.totalSales / b.totalSales percentage_of_prevous_month

FROM 
      cte a 
      INNER JOIN cte b 
      ON a.productname = b.productname
         and a.month = b.month - 1

少了一些碎片。如果除法的结果是一个小于0的数字，那么您可能实际上需要做一些事情，比如获得一个非零值

cast(a.totalSales as decimal)/ cast( b.totalSales  as decimal) 

另外，如果您的输入是一月，那么像这样使用月份输入也会导致问题。因此，最好将DateTimeReceived标准化为每月的第一天

e、 g

修改了选择和分组方式

   CONVERT(VARCHAR(25),DATEADD(dd,-(DAY(@mydate)-1),datetimerecieved),101) m

修改在哪里

   CONVERT(VARCHAR(25),DATEADD(dd,-(DAY(datetimerecieved)-1),datetimerecieved),101)
                  in ( '2/1/2012', DateAdd(m,-1,'2/1/2012'))

修改

a.M > b.M

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已编辑：未阅读有关百分比列的位。这将返回4列：productName、currentMonth、previousMonth和percentChange。ISNULL函数用于防止“被零除”错误。您可以将其调整到一个进程中，只需传入CurrentYear和CurrentMonth参数，或者传入一个datetime参数，让它从中计算出月份/年份，或者甚至使用GETDATE（）而不传递任何参数

declare @CurrentYear int,
    @CurrentMonth int,
    @previousYear int,
    @previousMonth int

set @CurrentYear = 2012
set @CurrentMonth = 2

if @CurrentMonth = 1 begin
    set @previousMonth = 12
    set @previousYear = @CurrentYear - 1
end else begin
    set @previousMonth = @CurrentMonth - 1
    set @previousYear = @CurrentYear
end

select  productName,
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @CurrentYear
    and DATEPART(month, dateTimeReceived) = @CurrentMonth
    and o.productid = p.productid) as currentMonth,
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid) as previousMonth,
    convert(decimal(10, 2), 100*(
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @CurrentYear
    and DATEPART(month, dateTimeReceived) = @CurrentMonth
    and o.productid = p.productid) 
    -
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid)
    /
    NULLIF(
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid), 0))) as percentChange
from    product p

---

谢谢康拉德，如果月份是一月，我们该如何称呼年份？肖恩，谢谢！仅供参考，公式应转换为foo（十进制（10,2），100*（新旧）/旧）。你有一个paren在错误的地方，但是你是99.9%正确的，所以我把这个标记为答案。感谢您的帮助。NULLIF使用得很好，但是select子句的内联视图表现糟糕，在这种情况下完全没有必要。此外，这将包括所有产品，即使它们没有订购。不确定这对手术是好是坏。

declare @CurrentYear int,
    @CurrentMonth int,
    @previousYear int,
    @previousMonth int

set @CurrentYear = 2012
set @CurrentMonth = 2

if @CurrentMonth = 1 begin
    set @previousMonth = 12
    set @previousYear = @CurrentYear - 1
end else begin
    set @previousMonth = @CurrentMonth - 1
    set @previousYear = @CurrentYear
end

select  productName,
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @CurrentYear
    and DATEPART(month, dateTimeReceived) = @CurrentMonth
    and o.productid = p.productid) as currentMonth,
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid) as previousMonth,
    convert(decimal(10, 2), 100*(
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @CurrentYear
    and DATEPART(month, dateTimeReceived) = @CurrentMonth
    and o.productid = p.productid) 
    -
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid)
    /
    NULLIF(
    (select COUNT(*) 
    from    [order] o 
    where   DATEPART(year, dateTimeReceived) = @previousYear
    and DATEPART(month, dateTimeReceived) = @previousMonth
    and o.productid = p.productid), 0))) as percentChange
from    product p