SQL 列转行的实现

--列转行，逗号拼接指定列的值

SQL Server中写法：
SELECT STUFF(( SELECT  ',' + Field1 from TableA FOR XML PATH('')), 1, 1, '')

Oracle中写法：

方法一：wmsys.wm_concat
select wmsys.wm_concat(Field1) from TableA

方法二：LISTAGG()

2.1、LISTAGG(XXX,XXX) WITHIN GROUP( ORDER BY XXX)

用法就像聚合函数一样，通过Group by语句，把每个Group的一个字段，拼接起来

with temp as(
  select 'China' nation,'Beijing' city from dual union
  select 'China' nation,'Shanghai' city from dual union
  select 'China' nation,'Guangzhou' city from dual union
  select 'USA' nation,'New York' city from dual union
  select 'USA' nation,'Bostom' city from dual
)
select nation,listagg(city,',') within group(order by city)
from temp
group by nation;

2.2、over(partition by XXX)

在不使用Group by语句时候，使用LISTAGG函数（当作SUM()函数来使用）

with temp as(
  select 'China' nation,'Beijing' city from dual union
  select 'China' nation,'Shanghai' city from dual union
  select 'China' nation,'Guangzhou' city from dual union
  select 'USA' nation,'New York' city from dual union
  select 'USA' nation,'Bostom' city from dual
)
select nation,city,listagg(city,',') within group(order by city) over(partition by nation) rank
from temp;