在 SQL 中计算累计总计

如何编写一个查询，在 SQL Server 中使用示例计算累计总计。对于这个经常被问到的面试问题，我们将使用下面展示的数据。

计算累计总计示例

在此示例中，我们将向您展示如何使用 子查询 来查找累计总计。

SELECT [FirstName]
      ,[LastName]
      ,[Education]
      ,[Occupation]
      ,[YearlyIncome]
      ,(
	 SELECT SUM(CUST2.[YearlyIncome]) 
         FROM [NewCustomers] AS CUST2
         WHERE CUST2.[CustID] <= CUST1.[CustID]
	) AS [Running Total]
  FROM [NewCustomers] AS CUST1

此示例显示如何使用 JOIN、GROUP BY 和 ORDER BY 子句来计算累计总计。

SELECT CUST1.[CustID]
      ,CUST1.[FirstName]
      ,CUST1.[LastName]
      ,CUST1.[Education]
      ,CUST1.[Occupation]
      ,CUST1.[YearlyIncome]
      ,SUM(CUST2.[YearlyIncome]) AS [Running Total]
FROM [NewCustomers] AS CUST1,
     [NewCustomers] AS CUST2	   
WHERE CUST2.[CustID] <= CUST1.[CustID]
GROUP BY CUST1.[CustID]
	,CUST1.[FirstName]
        ,CUST1.[LastName]
        ,CUST1.[Education]
        ,CUST1.[Occupation]
        ,CUST1.[YearlyIncome]
ORDER BY CUST1.[CustID]

在此 Server 示例中，我们将使用 SUM 函数和 OVER 来查找累计总计。

SELECT [FirstName]
      ,[LastName]
      ,[Education]
      ,[Occupation]
      ,[YearlyIncome]
      ,SUM([YearlyIncome]) OVER (
			          ORDER BY  [CustID]
				) AS [Running Total]
  FROM [NewCustomers]

并且更传统的方法是

SELECT [FirstName]
      ,[LastName]
      ,[Education]
      ,[Occupation]
      ,[YearlyIncome]
      ,SUM([YearlyIncome]) OVER (
			          ORDER BY  [CustID] ROWS UNBOUNDED PRECEDING
				) AS [Running Total]
  FROM [NewCustomers]