Question

ROW_NUMBER()仅用于SELECT中的MS SQL Server子句，但我想将其用于更新，如下所示：

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。

如何在ROW_NUMBER()子句中使用UPDATE？

Answer 1

您可以使用CTE：

;WITH RowNbrs AS (
    SELECT  ID
            , ROW_NUMBER() OVER (ORDER BY ID) AS RowNbr
    FROM    MyTab
    WHERE   a = b
)
UPDATE  t 
SET     t.MyNo = 123 +  r.RowNbr
FROM    MyTab t
        JOIN RowNbrs r ON t.ID = r.ID;

Answer 2

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

Answer 3

我会使用CTE

WITH myUpdate ( myRowNumber )
AS
( 
    SELECT ROW_NUMBER() over (order by ID) As myRowNumber
    FROM MyTab
    WHERE a = b
 ) 

update MyTab 
set MyNo = 123 + myRowNumber
FROM myUpdate

您可以先执行

测试

select * from myUpdate

如何在UPDATE子句中使用ROW_NUMBER（）？

3 个答案: