找出上一行和当前行之间的差异

Question

我有一张表presenters

我想找到主持人薪水之间的差异。喜欢（Jason - Vicki，Jason - Tiff，Vicki - Tiff）。

我有以下代码

SELECT 
    P2.PNRFNAME, P1.PNRFNAME AS "pnrfname",
    P2.SALARY_YEARLY - P1.SALARY_YEARLY AS "salary difference" 
FROM 
    PRESENTERS P2
JOIN 
    PRESENTERS P1 ON P2.PNRFNAME > P1.PNRFNAME
ORDER BY 
    "salary difference"

这些是结果

但我想要以下结果

Answer 1

如果您的行按PRESENTERID排序，而不是P2.PNRFNAME > P1.PNRFNAME，则可以使用PRESENTERID。

尝试;

SELECT P2.PNRFNAME ,P1.PNRFNAME AS "pnrfname" , P2.SALARY_YEARLY - P1.SALARY_YEARLY AS "salary difference" 
FROM PRESENTERS P2
INNER JOIN PRESENTERS P1
ON P2.PRESENTERID> P1.PRESENTERID
ORDER BY P2.PRESENTERID, P1.PRESENTERID

Answer 2

您可以尝试以下代码：

WITH CTE
AS (
    SELECT rownum = ROW_NUMBER() OVER (
            ORDER BY PNRFNAME
            )
        ,PNRFNAME
        ,SALARY_YEARLY
    FROM PRESENTERS
    )
SELECT prev.PNRFNAME PreviousValue
    ,CTE.PNRFNAME
    ,prev.SALARY_YEARLY - CTE.SALARY_YEARLY AS SALARY_DIFF
FROM CTE
LEFT JOIN CTE prev ON prev.rownum = CTE.rownum - 1
GO

来源：How to Access the Previous Row and Next Row value in SELECT statement?