SQL Server ROW_NUMBER（）问题

Question

我正在使用row_number（）表达式，但没有得到预期的结果。 我有一个sql表，有些行是重复的。 它们具有相同的“ BATCHID”，我想为它们获取第二行号，对于其他人，我使用第一行号。 我该怎么做？

SELECT * FROM (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t 
WHERE Rn=1

这段代码仅向我返回第一行，但我想为重复项获得第二行。

Answer 1

ROW_NUMBER()为每一行赋予唯一的计数器。 您想使用RANK() ，这很相似，但是给具有相同值的行赋予相同的分数：

SELECT * 
FROM   (SELECT * , RANK() OVER (PARTITION BY batchid ORDER BY scaqry) rk 
        FROM   sayimdcpc) t 
WHERE  rk = 1

Answer 2

如果某些值仅显示一次，而某些值显示两次（也许两次以上），则您不希望“第一”行，而想要“ max”行。 尝试逆转您的订单条件：

SELECT * 
FROM (SELECT * , 
             ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY DESC) Rn 
      FROM SAYIMDCPC ) t 
WHERE Rn=1

附带说明一下，最好将所有列都明确列出。 例如，您可能不需要此查询之外的Rn ...

Answer 3

只需尝试一下，

SELECT * FROM (SELECT * , ROW_NUMBER() OVER (ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t 
WHERE Rn=1

Answer 4

请尝试这个。 它将选择最大行数，如果没有重复，则应为第一个，否则为第二个

select * from (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) d,
(SELECT batchid,max(Rn) maxRn FROM (SELECT * , ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn FROM SAYIMDCPC ) t 
group by batchid) q 
where d.batchid = q.batchid and d.rn = q.maxrn

Answer 5

换句话说，这听起来像是在说：“当批次ID有一行时，请返回该行。如果有2行或更多行，请返回第二行。” 这将需要检查您的Rn值以查看其最大值。 我认为您无法在单个查询中做到这一点。

所以我会尝试这样的事情：

WITH NumberedRows AS (
    SELECT * , 
          ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) Rn 
    FROM SAYIMDCPC 
) 
,   MaxNumber AS (
    SELECT Max(RN) as MaxRn,
          BATCHID
    FROM NumberedRows
    GROUP BY BATCHID
)
,   NonDupes AS (
    SELECT *
    FROM  NumberedRows
    WHERE BATCHID NOT IN (SELECT BATCHID FROM MaxNumber WHERE MaxNumber = 1)
)
,   SecondRows AS (
    SELECT (
    FROM NumberedRows
    WHERE BATCHID NOT IN (SELECT BATCHID FROM MaxNumber WHERE MaxNumber > 1)
      AND Rn = 2
   )
SELECT 
FROM   NonDupes
UNION ALL
SELECT *
FROM   SecondRows

Answer 6

包含重复项和不重复项的总结果集。 第一列“ IsDuplicate”指示该列是否重复。

;WITH d1 AS (
    SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) 
          ,*
    FROM SAYIMDCPC
)

SELECT  IsDuplicate = CONVERT(BIT, Seq)
       ,* 
FROM d1

这只会给您重复项：

;WITH d1 AS (
    SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) 
          ,*
    FROM SAYIMDCPC
)

SELECT  IsDuplicate = CONVERT(BIT, Seq)
       ,* 
FROM d1
WHERE Seq > 1

这只会给您非重复项（如您的第一个查询）

;WITH d1 AS (
    SELECT Seq = ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY) 
          ,*
    FROM SAYIMDCPC
)

SELECT  IsDuplicate = CONVERT(BIT, Seq)
       ,* 
FROM d1
WHERE Seq = 1

Answer 7

如果我错了请纠正我

e.g sample data

BatchID, SCAQTY
  1    ,  10
  2    ,  10
  2    ,  20
  2    ,  30

您的期望结果如下吗？

**Expectation Result 1**
BatchID , SCAQty
 1      ,  10
 2      ,  30

要么

**Expectation Result 2**
BatchID , SCAQty
  1     ,   10
  2     ,   20
  2     ,   30

根据我的理解，您想要执行的是期望结果1，所以我想下面的查询应该可以帮助您，您只需要在查询中添加SCAQTY的desc

SELECT * FROM (SELECT * , 
ROW_NUMBER() OVER (PARTITION BY BATCHID ORDER BY SCAQTY DESC) Rn FROM SAYIMDCPC ) t 
WHERE Rn=1