Sql 获取没有重复数据的值

我有这样一个问题：

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

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

它返回的值如下：

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

我想做的是找到重复的

LegacyKeys

，并只获取一次legacyKey存在的值，因此我使用

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

但这返回的是错误的数据，因为它再次返回LegacyKey=17134，期望的结果是得到LegacyKey存在一次的值

所以欲望的结果应该是唯一的

  18017 |            7 

---

我做错了什么？

你需要这样的东西：

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

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

或

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

您可以简单地执行以下操作：

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。

第一个查询有三个输出列，但结果集只显示两个。有些不正确。抱歉，修复了@searle1986tbl1是否有主键，然后执行内部选择：）