Oracle 列转行函数 Listagg()

这是一个Oracle的列转行函数：LISTAGG()

 

先看示例代码：

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

 这是最基础的用法：

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。

非常方便。

 

同样是聚合函数，还有一个高级用法：

就是over(partition by XXX)

也就是说，在你不实用Group by语句时候，也可以使用LISTAGG函数：

with temp as(
  select 500 population, 'China' nation ,'Guangzhou' city from dual union all
  select 1500 population, 'China' nation ,'Shanghai' city from dual union all
  select 500 population, 'China' nation ,'Beijing' city from dual union all
  select 1000 population, 'USA' nation ,'New York' city from dual union all
  select 500 population, 'USA' nation ,'Bostom' city from dual union all
  select 500 population, 'Japan' nation ,'Tokyo' city from dual 
)
select population,
       nation,
       city,
       listagg(city,',') within GROUP (order by city) over (partition by nation) rank
from temp

 

总结：LISTAGG()把它当作SUM()函数来使用就可以了。

 

 

 

 

评论

5 楼 pktangshao 2017-03-08  

a_bun 写道

iijjll 写道

使用wmsys.wm_concat()函数也行

with temp as( 
  select 'China' nation ,'Guangzhou' city from dual union all 
  select 'China' nation ,'Shanghai' city from dual union all 
  select 'China' nation ,'Beijing' city from dual union all 
  select 'USA' nation ,'New York' city from dual union all 
  select 'USA' nation ,'Bostom' city from dual union all 
  select 'Japan' nation ,'Tokyo' city from dual  
) 
select nation,wmsys.wm_concat(city)
from temp 
group by nation

wm_concat函数慎用，性能很差，会产生很多block的

wm_concat实在是少用为好,今天是遇到了,SQL中执行很快,到了存储过程超级慢.慢10倍以上.找了好久才找到原来是这个函数这里慢
谢谢博主提供的这个LISTAGG函数.
本来我在最后GROUP的,看了楼主的写法改造成OVER(PARTITAION BY)了,在同样的数据情况下比在最后GROUP快了6秒.

4 楼 a_bun 2016-08-11  

iijjll 写道

使用wmsys.wm_concat()函数也行

with temp as( 
  select 'China' nation ,'Guangzhou' city from dual union all 
  select 'China' nation ,'Shanghai' city from dual union all 
  select 'China' nation ,'Beijing' city from dual union all 
  select 'USA' nation ,'New York' city from dual union all 
  select 'USA' nation ,'Bostom' city from dual union all 
  select 'Japan' nation ,'Tokyo' city from dual  
) 
select nation,wmsys.wm_concat(city)
from temp 
group by nation

wm_concat函数慎用，性能很差，会产生很多block的

3 楼 iijjll 2015-01-20  

使用wmsys.wm_concat()函数也行

with temp as( 
  select 'China' nation ,'Guangzhou' city from dual union all 
  select 'China' nation ,'Shanghai' city from dual union all 
  select 'China' nation ,'Beijing' city from dual union all 
  select 'USA' nation ,'New York' city from dual union all 
  select 'USA' nation ,'Bostom' city from dual union all 
  select 'Japan' nation ,'Tokyo' city from dual  
) 
select nation,wmsys.wm_concat(city)
from temp 
group by nation

2 楼 dacoolbaby 2013-01-15  

Eric.Yan 写道

listagg作为分析函数（即实用over(partition by XXX)关键字）用到的很少，楼主的sql：
select population,  
       nation,  
       city,  
       listagg(city,',') within GROUP (order by city) over (partition by nation) rank  
from temp;

意思是选出跟当前city一样的属于同一个nation的city,合并显示；

你说的没错。
使用或不使用over(partition by xxx)根据你的SQL的复杂度来进行判断。

1 楼 Eric.Yan 2013-01-15  

listagg作为分析函数（即实用over(partition by XXX)关键字）用到的很少，楼主的sql：
select population,  
       nation,  
       city,  
       listagg(city,',') within GROUP (order by city) over (partition by nation) rank  
from temp;

意思是选出跟当前city一样的属于同一个nation的city,合并显示；