sql - 分组依据并添加列

我有一张名为“沃德议员”的桌子和两列“沃德”和“议员”。这张表列有所有议员及其负责的病房的名单。每个病房有三名议员，我需要做的是分组，以便我有一个不同的记录，每个病房和三个新的专栏，三名议员负责每个病房。
例如，目前有：

WARD   | COUNCILLOR
ward a | cllr 1
ward a | cllr 2
ward a | cllr 23
ward b | cllr 4
ward b | cllr 5
ward b | cllr 8

努力实现：

WARD    | COUNCILLOR 1| COUNCILLOR 2| COUNCILLOR 3
ward a  | cllr 1      | cllr 2      | cllr 23
ward b  | cllr 4      | cllr 5      | cllr 8

提前谢谢你，
克里斯

最佳答案

我倾向于使用条件聚合来处理此类查询：

select ward,
       max(case when seqnum = 1 then councillor end) as councillor1,
       max(case when seqnum = 2 then councillor end) as councillor2,
       max(case when seqnum = 3 then councillor end) as councillor3
from (select wc.*,
             row_number() over (partition by ward order by councillor) as seqnum
      from ward_councillors wc
     ) wc
group by ward;

关于sql - 分组依据并添加列，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28853708/