Oracle中的listagg

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 over(partition by XXX)，在不使用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  

 


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