在另一列中的一组行中选择一列的第一行答案

【问题标题】：Select the first row of a column in a group of rows within another column在另一列中的一组行中选择一列的第一行
【发布时间】：2020-11-01 03:46:47
【问题描述】：

我必须在另一列的一组行中显示一列第一行的列表

基本查询：

SELECT * FROM Table_Example cxp

我的桌子

    |plan   |code   |des   |month   |
----+-------+-------+------+--------+
    | 150B  | Alpha | etc.a| 1      |
----+-------+-------+------+--------+
    | 150B  | Beta  | etc.b| 2      |
----+-------+-------+------+--------+
    | 2600C | Alpha | etc.a| 6      |
----+-------+-------+------+--------+
    | 2600C | Alpha | etc.a| 7      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 3      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 7      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 9      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 2      |
----+-------+-------+------+--------+
    | 2600C | Gama  | etc.c| 4      |
----+-------+-------+------+--------+
    | 2600C | Gama  | etc.c| 12     |
----+-------+-------+------+--------+
    | 2600C | Delta | etc.d| 22     |
----+-------+-------+------+--------+
    | 42F   | Alpha | etc.a| 15     |

预期结果

    |plan   |code   |des   |month   |
----+-------+-------+------+--------+
    | 2600C | Alpha | etc.a| 6      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 3      |
----+-------+-------+------+--------+
    | 2600C | Gama  | etc.g| 4      |
----+-------+-------+------+--------+
    | 2600C | Delta | etc.d| 22     |
----+-------+-------+------+--------+

成绩单结果：具有变量“@plan”，仅显示与该值匹配的行（例如：如果“@plan”为 2600C）并且在该组行中，仅显示每个不同“代码”值的第一行

我想做什么

SELECT * FROM Table_Example cxp WHERE plan = '2600C'

    |plan   |code   |des   |month   |
----+-------+-------+------+--------+
    | 2600C | Alpha | etc.a| 6      |
----+-------+-------+------+--------+
    | 2600C | Alpha | etc.a| 7      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 3      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 7      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 9      |
----+-------+-------+------+--------+
    | 2600C | Beta  | etc.b| 2      |
----+-------+-------+------+--------+
    | 2600C | Gama  | etc.c| 4      |
----+-------+-------+------+--------+
    | 2600C | Gama  | etc.c| 12     |
----+-------+-------+------+--------+
    | 2600C | Delta | etc.d| 22     |

但我不能只得到每个不同“代码”的第一行我在考虑一个子查询，但我尝试了很多，但我无法得到正确的结果或者它只返回“代码”列而不返回其他列，例如：

|code   |
+-------+
| Alpha |     
+-------+
| Beta  |       
+-------+
| Gama  |      
+-------+
| Delta |      
+-------+

【问题讨论】：

标签： sql sql-server

【解决方案1】：

您可以使用row_number()

select * from
(
  SELECT *,row_number() over(partition by code order by month) as rnk
  FROM Table_Example cxp
  WHERE plan = '2600C'
)A where rnk=1

【讨论】：