Oracle SQL：如何合并 n 行并在结果中创建附加列？

Question

表：

id race
1  elf
1  troll
2  lizard
2  elf
2  human    
3  dwarf

我正在寻找输出以下内容的请求：

id race1   race2   race3
1  elf     troll   
2  lizard  elf     human
3  dwarf

如果更容易的话，可以有 n 场比赛或给定的最大比赛数

这可以通过 sql 查询（不是 pl/sql）实现吗？ (oracle 如果需要特殊功能)

Answer 1

如果您想在简单的select 中执行此操作，可以使用条件聚合：

select id,
       max(case when seqnum = 1 then race end) as race_1,
       max(case when seqnum = 2 then race end) as race_2,
       max(case when seqnum = 3 then race end) as race_3,
       max(case when seqnum = 4 then race end) as race_4,
       max(case when seqnum = 5 then race end) as race_5
from (select t.*,
             row_number() over (partition by id order by id) as seqnum
      from t
     ) t
group by id;