SQL中RowNum的有条件选择

Question

我已经写了一个查询，它返回下列数据。

ID EmpFirstName EmpLastName RowNum 
1  X     Y  1 
2  A     B  1 
3  A     B  2 

现在我想要RowNum> 1的所有记录。例如，在这种情况下，我需要输出2和3记录。

如果我把条件RowNum >1然后我只会得到第三条记录，但我也想要2。

Answer 1

假设你的查询是这样的：

select ID, EmpFirstName, EmpLastName, 
ROW_NUMBER() OVER (PARTITION BY EmpFirstName, EmpLastName ORDER BY ID) AS RowNum 
FROM aTable 

这是用来过滤掉任何重复值的经典查询。

为了有效地选择所有重复值的记录，我可以建议使用COUNT（）窗口功能：

;with a as (
    select ID, EmpFirstName, EmpLastName, 
    ROW_NUMBER() OVER (PARTITION BY EmpFirstName, EmpLastName ORDER BY ID) AS RowNum, 
    COUNT(*) OVER (PARTITION BY EmpFirstName, EmpLastName) AS cnt 
    FROM aTable 
) 
SELECT * FROM a where cnt > 1 
ORDER BY EmpFirstName, EmpLastName 

为了测试它使用此查询：

drop table #tmp 
CREATE table #tmp (ID int , EmpFirstName varchar(10) , EmpLastName varchar(10)) 
go 
INSERT INTO #tmp VALUES 
    (1,'X','Y') 
    ,(2,'A','B') 
    ,(3,'A','B') 
    ,(4,'A','C') 
    ,(5,'B','C') 
    ,(6,'B','C') 


;with a as (
    select ID, EmpFirstName, EmpLastName, 
    ROW_NUMBER() OVER (PARTITION BY EmpFirstName, EmpLastName ORDER BY ID) AS RowNum, 
    COUNT(id) OVER (PARTITION BY EmpFirstName, EmpLastName) AS cnt 
    FROM #tmp 
) 
SELECT * FROM a where cnt > 1 
ORDER BY EmpFirstName, EmpLastName 

结果：

ID   EmpFirstName EmpLastName RowNum    cnt 
----------- ------------ ----------- -------------------- ----------- 
2   A   B   1     2 
3   A   B   2     2 
5   B   C   1     2 
6   B   C   2     2 

Answer 2

我制作样本数据并使用此查询

CREATE table #tmp (ID int , EmpFirstName varchar(10) , EmpLastName varchar(10) ,RowNum int) 
INSERT INTO #tmp VALUES 
    (1,'X','Y',1) 
    ,(2,'A','B',1) 
    ,(3,'A','B',2) 

SELECT ID,EmpFirstName,EmpLastName,RowNum 
FROM (
    SELECT * 
     ,ROW_NUMBER() OVER (ORDER BY ID) AS [NEWrownum] 
    FROM #tmp 
) q 
WHERE q.NEWrownum > 1 

Answer 3

试试这个，

DECLARE @Result TABLE (ID INT, EmpFirstName VARCHAR(10), EmpLastName VARCHAR(10), RowNum INT) 

INSERT INTO @Result 
VALUES 
    (1, 'X', 'Y', 1) 
    ,(2, 'A', 'B', 1) 
    ,(3, 'A', 'B', 2) 

SELECT r1.* 
FROM @Result r1 
INNER JOIN (SELECT *  -- get duplicate records 
      FROM @Result 
      WHERE RowNum = 2     
      ) as r2 ON r1.EmpFirstName = r2.EmpFirstName 
        AND r1.EmpLastName = r2.EmpLastName