从一组相同的 table 中减去值

Question

Year          Month    Code         Value
2021        January     201         100.00
2021        February    201         250.00
2021        January     202         300.00
2021        February    202         200.00
2021        March       201         50.00
2021        March       202         150.00

需要从 202 中减去代码 201 ，将两个代码按月分组。输出：

Year     Month     Value 
2021    january     200 
2021    february    -50
2021     March       100

我试图获得所需的输出，但它不起作用..

SELECT Code,Value
    ,
    (
        SELECT sum(Value) as Value
        FROM [TestD]
        Where Code = '202'
        GROUP BY Code
        )-(
        SELECT sum(Value) as Value
        FROM [TestD]
        where Code = '201'
        GROUP BY Code
        )  AS item_total

FROM [TestD] group by Code,Value

Answer 1

您可以在 sum(...) 中使用 case 表达式，其中 group by Year, Month:

select Year, 
Month,
sum(case when Code = '201' then -Value when Code = '202' then Value end) as Value
from TestD
group by Year, Month

Fiddle

Answer 2

如果只减去 2 个值，您可以试试这个

declare @tbl table (year int, [month] varchar(50),code int, [value] int)

insert into @tbl values(2021, 'January', 201, 100.00),(2021, 'Feb', 201, 250.00)
,(2021, 'January', 202, 300.00),(2021, 'Feb', 202, 200.00)


select year,[month],[value], row_number()over(partition by [month] order by [value] desc) rownum
into #temp
from @tbl

select year,
month
,case when rownum = 1 then value else (
(select value from #temp t1 where t1.[month] = t.[month] and t1.rownum = 1) - 
value) end as diff
from #temp t
where t.rownum = 2
order by month desc

drop table #temp

从一组相同的 table 中减去值

Subtract value from group of same table

sql

tsql

sql-server