如何在 UPDATE 子句中使用 ROW_NUMBER()? [英] How to use ROW_NUMBER() in UPDATE clause?

问题描述

ROW_NUMBER() 仅用于 MS SQL Server 中的 SELECT 子句，但我想用它来更新以下:

ROW_NUMBER() is only for used in the SELECT clause in MS SQL Server, but I want to use it for update like the following:

Update MyTab Set MyNo = 123 +  ROW_NUMBER() over (Order By ID)
Where a=b;

然后我得到了错误，

窗口函数只能出现在 SELECT 或 ORDER BY 子句中.

Windowed functions can only appear in the SELECT or ORDER BY clauses.

如何在UPDATE子句中使用ROW_NUMBER()?

推荐答案

DECLARE @MyTable TABLE
(
    ID INT IDENTITY(2,2) PRIMARY KEY,
    MyNum INT,
    ColA INT,
    ColB INT
);

INSERT  @MyTable (ColA, ColB)
SELECT 11, 11 UNION ALL
SELECT 22, 22 UNION ALL
SELECT NULL, NULL UNION ALL
SELECT 33, NULL UNION ALL
SELECT NULL, 44 UNION ALL
SELECT 55, 66;

UPDATE  UpdateTarget
SET     MyNum = RowNum
FROM
(
    SELECT  x.MyNum, ROW_NUMBER() OVER(ORDER BY x.ID) AS RowNum
    FROM    @MyTable x
    WHERE   x.ColA = x.ColB
) AS UpdateTarget;

SELECT * FROM @MyTable;

结果:

ID          MyNum       ColA        ColB
----------- ----------- ----------- -----------
2           1           11          11
4           2           22          22
6           NULL        NULL        NULL
8           NULL        33          NULL
10          NULL        NULL        44
12          NULL        55          66

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