获取 INNER JOIN 中值的 SUM 会添加重复值

Question

我是运行一个查询，它每月从 table 中计算记录。我正在尝试添加一个名为 "TotalPrice" 的额外列，我需要 'settle' table.

中所有价格的总和

我面临的问题是因为 INNER JOIN，'SUM' 的价格由于 INNER JOIN 返回的重复记录而累加了多个价格。有没有办法避免它并从唯一记录中获取价格总和？

SELECT
CONCAT(year(datetime), '-', month(datetime)) AS YearMonth,
COUNT (DISTINCT a.id) AS TOTAL, SUM(total_price) AS TotalPrice
FROM settle AS a with (nolock)
     INNER JOIN transfers b with (nolock) ON b.settleId = a.id 
     INNER JOIN Fdata AS c with (nolock) ON c.id=  b.data 
GROUP BY CONCAT(year(datetime), '-', month(datetime))

提前致谢。

Answer 1

sql 服务器 2008 之后：

with CTE as -- A CTE alows us to manipulate the data before we use it, like a derived table
(
select datetime, id, total_price, 
       row_number() over(partition by id, datetime order by total_price) as rn -- This creates a row number for each combo of id and datetime that appears
FROM settle AS a with (nolock)
     INNER JOIN transfers b with (nolock) ON b.settleId = a.id 
     INNER JOIN Fdata AS c with (nolock) ON c.id=  b.data 
)
SELECT CONCAT(year(datetime), '-', month(datetime)) AS YearMonth,
       COUNT (DISTINCT a.id) AS TOTAL, 
       SUM(total_price) AS TotalPrice
from CTE
where rn = 1 -- that row_number we created? This selects only the first one, removing duplicates
group by CONCAT(year(datetime), '-', month(datetime))

获取 INNER JOIN 中值的 SUM 会添加重复值

Getting a SUM of the values in INNER JOIN adds up duplicate values

sql

sql-server

sql-server-2008

sql-server-2005