获取没有重复数据的值

Question

我有这样的查询：

SELECT
      P.LegacyKey
      ,D.DesignNumber
      FROM tbl1 AS [SO]
 GROUP BY D.DesignNumber,P.LegacyKey
 ORDER BY LegacyKey

它返回的值如下：

+-----------+--------------+
| LegacyKey | DesignNumber |
+-----------+--------------+
|     17134 |            1 |
|     17134 |            2 |
|     18017 |            7 |
+-----------+--------------+

我想要做的是找到重复的LegacyKeys并只获取legacyKey存在一次的值，所以我使用HAVING COUNT：

SELECT
      P.LegacyKey
      ,D.DesignNumber
      , COUNT([P].[LegacyKey])
      FROM tbl1 AS [SO]
 GROUP BY D.DesignNumber,P.LegacyKey
 HAVING COUNT([P].[LegacyKey])  = 1
 ORDER BY LegacyKey

但是这会返回错误的数据，因为它再次返回LegacyKey = 17134，并且希望结果是获取LegacyKey存在一次的值。

所以欲望结果应该只是

  18017 |            7 

我究竟做错了什么？

Answer 1

你可以简单地做：

SELECT P.LegacyKey, MAX(D.DesignNumber) as DesignNumber
FROM tbl1 AS [SO]
GROUP BY P.LegacyKey
HAVING COUNT(DISTINCT D.DesignNumber) = 1;
ORDER BY LegacyKey;

不需要子查询。

Answer 2

你需要这样的东西：

select t2.LegacyKey, t2.DesignNumber
from
(
    select t.LegacyKey 
    from tbl1 t
    group by t.LegacyKey 
    having count(t.LegacyKey ) = 1
)x
join tbl1 t2 on x.LegacyKey = t2.LegacyKey

要么

select t2.LegacyKey, t2.DesignNumber
from tbl1 t2
where t2.LegacyKey in
(
    select t.LegacyKey 
    from tbl1 t
    group by t.LegacyKey 
    having count(t.LegacyKey ) = 1
)

Answer 3

你可以试试这个

注意 - 这是未经测试的

SELECT  *   
FROM    (
            SELECT
                  P.LegacyKey AS LegacyKey,
                  D.DesignNumber AS DesignNumber,
                  COUNT([P].[LegacyKey]) AS cnt
             FROM tbl1 AS [SO]
             GROUP BY D.DesignNumber,P.LegacyKey
             HAVING COUNT([P].[LegacyKey])  = 1
        ) a
WHERE   COUNT() OVER (PARTITION BY LegacyKey) = 1