Question

我正在使用SQL Server 2008R2，并且有一个名为AirNewformat的表。这个表主要由ID列搜索，该列有许多重复项。我想通过添加一个名为processed的列来更新同一个表，其中ID的第一个值在处理列中更新为'N'，其余的重复项在处理列中更新为'D'。目前，我已将所有记录更新为N或D，但我希望看到如下例所示的更新。非常感谢任何帮助。

ID       Processed
---       ---------
12       N
12       D
12       D
13       N
13       D
13       D

Answer 1

请尝试使用此代码（ SQL小提琴： http://sqlfiddle.com/#!3/03991/6 ）：

将每个ID组中的第一条记录更新为N：

UPDATE 
  A
SET
  A.Processed = 'N'
FROM
  (
     SELECT ID, Processed, ROW_NUMBER() OVER(ORDER BY ID) AS row_num FROM AirNewformat
  ) AS A
  INNER JOIN 
  (
     SELECT
         C.ID,
         MIN(C.row_num) AS min_row_num
     FROM
     (
       SELECT ID, ROW_NUMBER() OVER(ORDER BY ID) AS row_num FROM AirNewformat
     ) AS C
     GROUP BY C.ID
  ) AS B ON A.ID = B.ID AND A.row_num = B.min_row_num;

将所有其余记录更新为D：

UPDATE 
  AirNewformat
SET
  AirNewformat.Processed = 'D'
WHERE
  ISNULL(AirNewformat.Processed, '') = '';

Answer 2

你可以试试这个：

;with cte as
(
select ROW_NUMBER() over (PARTITION by ID order by ID) N, processed from airNewformat
)

update cte
set processed = case when N = 1 then 'N'
    when N >1 then 'D' end;

更新具有重复项的列

2 个答案: