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 '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,listaggcity,',') within GROUP order by city) from temp group by nation
登录后复制
这是最基础的用法：
LISTAGGXXX,XXX) WITHIN GROUP ORDER BY XXX)
登录后复制
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overpartition 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, '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,
listaggcity,',') within GROUP order by city) over partition by nation) rank
from temp
登录后复制
总结：LISTAGG)把它当作SUM)函数来使用就可以了。
以上就是listagg函数的用法的详细内容，更多请关注风君子博客其它相关文章！