选择多列计算一列并在一张表中按一列分组

Question

我有一个名为[delivery]的表，其[ID],[Employee],[Post],[c_name],[Deli_Date],[note]

我需要选择所有列并计算Employee ，然后按Employee分组。 表格中的数据如下所示：

  ---------------------------------------------------
  | Employee| Post      |c_name  |Deli_Date   |Note |
  |---------|-----------|---------------------|-----|
  |  DAVID  |MANAGER    | a      |11/11/2018  |note |
  |  DAVID  |MANAGER    | b      |01/01/2015  |note |
  |  SAM    |ACOUNTS    | c      |10/10/2016  |note |
  |  DAVID  |IT         | a      |10/02/2015  |note |
  |  DAVID  |DOCTOR     | c      |20/02/2017  |note |
  |  JAMES  |DELIVERYMAN| b      |05/05/2015  |note |
  |  OLIVER |DRIVER     | b      |02/02/2014  |note |
  |  SAM    |ACOUNTS    | c      |02/02/2012  |note |

此代码：

select Employee, count(Employee) as TIMES from delivery
group by Employee

结果是：（但是我也需要显示其他列）。

| Employee| TIMES | 
|---------|-------|
|  DAVID  |   4   |
|  JAMES  |   1   |
|  OLIVER |   1   |
|  SAM    |   2   |

我需要这样的代码显示：

| Employee| TIMES | Post      |c_name  |Deli_Date   |Note |
|---------|-------|-----------|---------------------|-----|
|  DAVID  |   4   |MANAGER    | a      |11/11/2018  |note |
|  JAMES  |   1   |DELIVERYMAN| b      |05/05/2015  |note |
|  OLIVER |   1   |DRIVER     | b      |02/02/2014  |note |
|  SAM    |   2   |ACOUNTS    | c      |10/10/2016  |note |

什么是最好的查询可以给我那个结果？

参见[c_name],[Deli_Date]列[c_name],[Deli_Date]它们显示了最后插入的数据。 或者只给我没有[c_name],[Deli_Date]的结果就可以了。

Answer 1

如果需要最后一个日期和计数，则可以使用窗口功能：

select d.Employee, d.cnt, d.Post, d.c_name, d.Deli_Date, d.Note 
from (select d.*,
             count(*) over (partition by employee) as cnt,
             row_number() over (partition by employee order by deli_date desc) as seqnum
      from delivery d
     ) d
where seqnum = 1;

Answer 2

select Employee, count(Employee) as TIMES,Post,c_name,Deli_Date,Note from delivery
group by Employee

Answer 3

您需要在select和group by子句中包括所有未聚合的列

select Employee,
  count(Employee) as TIMES,
  max(Deli_date) as LAST_DELI_DATE,
  post,
  note
from delivery
group by Employee, post, note

Max（Deli_date）将为您提供最新日期。

要获取最新的c_name，注释，帖子等，您将需要一个带有按deli_date排序的rank函数的子查询。 稍后将添加示例。