从Resultset获取不同的值

Question

我有下表Employee和记录如下：

Eid      Ename     Phone
------------------------     
 1         A        043
 1         A        067
 2         B        073
 2         B        072
 3         C        753 
 3         C        464

到目前为止我得到了什么：

SELECT *
FROM   (SELECT Row_number() OVER (ORDER BY Eid ASC) AS rownum,
               Eid,
               Ename,
               Phone
        FROM   Employee
        WHERE  Eid IN(SELECT DISTINCT(Eid)
                      FROM   Employee
                      GROUP  BY Eid)) AS RESULTSET
WHERE  rownum BETWEEN 0 AND 3

实际上，内部查询会返回distinct结果，但是当我在最终RESULTSET获得结果时，它不会反映出来。

请告知如何获得独特的结果。我的输出应该如下所示：

Eid      Ename     Phone
------------------------     
 1         A         043
 2         B         073
 3         C         753

Answer 1

如果使用QUALIFY子句，则可以指定要返回的Row_Number值范围。 QUALIFY子句用于窗口聚合函数HAVING子句与非窗口聚合函数的对比。

SELECT DISTINCT
       e1.eid
     , e1.ename
     , e1.ephone
--     , ROW_NUMBER() OVER(PARTITION BY e1.eid ORDER BY e1.eid) AS RowNum_
FROM emp e1
QUALIFY ROW_NUMBER() OVER(PARTITION BY e1.eid ORDER BY e1.eid) = 1

如果您在结果集中包含RowNum_，则可以在QUALIFY而不是ROW_NUMBER()窗口聚合中再次引用它。

Answer 2

您的查询要复杂得多。尝试使用CROSS APPLY

进行简化

SELECT DISTINCT a.Eid, a.Ename, c.Phone
FROM   EMPLOYEE a
CROSS APPLY
(
  SELECT  TOP 1 ROW_NUMBER() OVER (PARTITION by Ename ORDER BY Eid ASC) AS RowNo,
          b.Eid, b.Phone
  FROM    EMPLOYEE b
  WHERE   a.EID = b.eid 
  ORDER BY RowNo ASC                         -- you can change this to DESC also
) c

我添加DISTINCT的原因是因为您要自己加入表格。

另一个更简单的版本

SELECT DISTINCT a.Eid, a.Ename, c.Phone
FROM   EMPLOYEE a
CROSS APPLY
(
  SELECT  TOP 1 b.Eid, b.Phone
  FROM    EMPLOYEE b
  WHERE   a.EID = b.eid 
) c

SQLFiddle Demo

Answer 3

啊，我不知道你想要这个查询，但不知怎的，我把它建在你的预期输出

代码：

select    Eid,Ename,Phone 
from      (select ROW_NUMBER() OVER (ORDER BY Eid ASC) AS rownum,
                  Eid,
                  Ename,
                  Phone 
           from Employee 
           where Eid in (select distinct(Eid) 
                         from Employee  )
         ) AS RESULTSET
Where rownum %2<>0

SQLFiddle Demo

Answer 4

试试这个

 SELECT * 
FROM   (SELECT Row_number() OVER (partition by ename ORDER BY Eid ASC) AS rownum, 
               Eid, 
               Ename, 
               Phone 
        FROM   Employeee
        WHERE  Eid IN(SELECT DISTINCT(Eid) 
                      FROM   Employeee
                      GROUP  BY Eid)) AS RESULTSET 
WHERE  rownum =1

Answer 5

试试这个：

 select Eid,Ename,Phone from 
 (select *,ROW_NUMBER() over(partition by Ename order by eid) as rn from emp) a
 where rn=1