listagg函数的用法-SQL-php.cn

listagg函数的用法

藏色散人

Lepaskan： 2020-05-06 15:21:07

asal

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listagg函数的用法

这是一个Oracle的列转行函数：LISTAGG()

先看示例代码：

Sql代码

with temp as(  
  select &#39;China&#39; nation ,&#39;Guangzhou&#39; city from dual union all  
  select &#39;China&#39; nation ,&#39;Shanghai&#39; city from dual union all  
  select &#39;China&#39; nation ,&#39;Beijing&#39; city from dual union all  
  select &#39;USA&#39; nation ,&#39;New York&#39; city from dual union all  
  select &#39;USA&#39; nation ,&#39;Bostom&#39; city from dual union all  
  select &#39;Japan&#39; nation ,&#39;Tokyo&#39; city from dual   
)  
select nation,listagg(city,&#39;,&#39;) within GROUP (order by city)  
from temp  
group by nation

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这是最基础的用法：

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

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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：

Sql代码

with temp as(  
  select 500 population, &#39;China&#39; nation ,&#39;Guangzhou&#39; city from dual union all  
  select 1500 population, &#39;China&#39; nation ,&#39;Shanghai&#39; city from dual union all  
  select 500 population, &#39;China&#39; nation ,&#39;Beijing&#39; city from dual union all  
  select 1000 population, &#39;USA&#39; nation ,&#39;New York&#39; city from dual union all  
  select 500 population, &#39;USA&#39; nation ,&#39;Bostom&#39; city from dual union all  
  select 500 population, &#39;Japan&#39; nation ,&#39;Tokyo&#39; city from dual   
)  
select population,  
       nation,  
       city,  
       listagg(city,&#39;,&#39;) within GROUP (order by city) over (partition by nation) rank  
from temp

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总结：LISTAGG()把它当作SUM()函数来使用就可以了。

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