plsql:在分组语句中获取另一个字段值以及聚合值

Question

我正在研究考勤系统.我将员工的交易存储在下表中:

我想获得每位员工的最早和最新交易,包括他们的日期和类型.

我可以使用分组和聚合来获取日期.但是,我无法弄清楚如何使用它们获取类型.

你能帮帮我吗？

谢谢.

Answer 1

这就是FIRST和LAST聚合函数的设计目标.

这是文档的链接:

首先:http://download.oracle.com/docs/cd/E11882_01/server.112/e17118/functions065.htm#SQLRF00641 最后:http://download.oracle.com/docs/cd/E11882_01/server.112 /e17118/functions083.htm#sthref1206

这是一个例子:

SQL> create table my_transactions (id,employee_id,action_date,type)
  2  as
  3  select 1, 1, sysdate, 'A' from dual union all
  4  select 2, 1, sysdate-1, 'B' from dual union all
  5  select 3, 1, sysdate-2, 'C' from dual union all
  6  select 4, 1, sysdate-3, 'D' from dual union all
  7  select 5, 2, sysdate-11, 'E' from dual union all
  8  select 6, 2, sysdate-12, 'F' from dual union all
  9  select 7, 2, sysdate-13, 'G' from dual
 10  /

Table created.

SQL> select *
  2    from my_transactions
  3   order by id
  4  /

        ID EMPLOYEE_ID ACTION_DATE         T
---------- ----------- ------------------- -
         1           1 04-07-2011 10:15:07 A
         2           1 03-07-2011 10:15:07 B
         3           1 02-07-2011 10:15:07 C
         4           1 01-07-2011 10:15:07 D
         5           2 23-06-2011 10:15:07 E
         6           2 22-06-2011 10:15:07 F
         7           2 21-06-2011 10:15:07 G

7 rows selected.

SQL> select employee_id
  2       , min(action_date) min_date
  3       , max(type) keep (dense_rank first order by action_date) min_date_type
  4       , max(action_date) max_date
  5       , max(type) keep (dense_rank last order by action_date) max_date_type
  6    from my_transactions
  7   group by employee_id
  8  /

EMPLOYEE_ID MIN_DATE            M MAX_DATE            M
----------- ------------------- - ------------------- -
          1 01-07-2011 10:15:07 D 04-07-2011 10:15:07 A
          2 21-06-2011 10:15:07 G 23-06-2011 10:15:07 E

2 rows selected.

问候,
Rob.