分组依据并添加列

问题描述

我倾向于使用条件聚合来处理这种类型的查询：

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;

解决方法

我有一个名为“ ward_councillors”的表，以及两列“ ward”和“
councillor”。该表包含所有议员和他们所负责的病房的列表。每个病房都有三名议员，我需要按小组进行分组，这样我每个病房都有一个独特的记录，并且有三个新的栏目，每个病房中都有三名议员负责。

例如当前有：

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

试图达到：

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

预先感谢克里斯

sql sql