Question

我有下表，其中包含有关每个小组如何解决问题的数据：

PROB | GROUP   | REPNO | STATUS
-----+---------+-------+-------
 1   | Juniors |    0  |
 1   | Seniors |    1  |
 1   | Juniors |    2  |
 1   | Experts |    3  | SOLVED
 2   | Juniors |    0  |
 2   | Seniors |    1  | SOLVED

列PROB定义了组正在解决的问题，列GROUP定义了哪个组正在处理此问题，列REPNO定义了解决重复的次数（重复尝试直到最终解决，0表示首次尝试，还没有重复），最后一列STATUS定义了在特定尝试中是否解决了任务。在这里，我可以分配ALL GROUPS（SELECT ... GROUP BY repno）在每次重复中如何有效地解决工作。

但我想展示每个特定群体如何有效地解决probs（每个群体的分布＆＃39;自己的重复顺序）。例如，PROB 1被组Juniors尝试了两次，一次被组Seniors尝试并且没有被解决，最后在小组专家的第一次尝试中解决了。

所以我需要重新计算每个特定组的重复次数：

PROB | GROUP   | REPNO | REPNO_J | REPNO_S | REPNO_E | STATUS
-----+---------+-------+---------+---------+---------+-------
 1   | Juniors |    0  |       0 |         |         |
 1   | Seniors |    1  |         |       0 |         |         
 1   | Juniors |    2  |       1 |         |         |        
 1   | Experts |    3  |         |         |       0 | SOLVED  <-- experts solved in first try
 2   | Juniors |    0  |       0 |         |         |
 2   | Seniors |    1  |         |       0 |         | SOLVED  <-- seniors solved in first try

如何重新计算？

Answer 1

使用ROW_NUMBER窗口函数获取每组的数量：

select 
  prob, 
  "GROUP", 
  repno,
  case when "GROUP" = 'Juniors' then try end as repno_j,
  case when "GROUP" = 'Seniors' then try end as repno_s,
  case when "GROUP" = 'Experts' then try end as repno_e,
  status
from
(
   select 
     prob, "GROUP", repno, status,
     row_number() over(partition by prob, "GROUP" order by repno) - 1 as try
   from mytable
)
order by prob, repno;

顺便说一句：命名列GROUP不是一个好主意。这是SQL中的保留字。因此，只要在查询中使用名称，就必须使用引号并考虑大小写。

Answer 2

USE RANK（） SQL FIDDLE

select 
  PROB, 
  GROUP1, 
  REPNO,
  DECODE(GROUP1,'Juniors', rank() over (partition by prob, group1 order by repno) - 1) as REPNO_J,
  DECODE(GROUP1,'Seniors', rank() over (partition by prob, group1 order by repno) - 1) as REPNO_S,
  DECODE(GROUP1,'Experts', rank() over (partition by prob, group1 order by repno) - 1) as REPNO_E,
  STATUS
from mytable
order by prob,repno

Answer 3

您可以使用CASE声明

SELECT "PROB", 
       "GROUP",
       "REPNO",
       (CASE WHEN  "GROUP" = 'Juniors' THEN REPNO ELSE NULL END ) as REPNO_J,
       (CASE WHEN  "GROUP" = 'Seniors' THEN REPNO ELSE NULL END ) as REPNO_S,
       (CASE WHEN  "GROUP" = 'Experts' THEN REPNO ELSE NULL END ) as REPNO_E
FROM Table1

在组内重新排序

3 个答案: