一、LISTAGG(XXX,XXX) WITHIN GROUP( ORDER BY XXX)
介绍:其函数在Oracle 11g 版本中推出,对分组后的数据按照一定的排序进行字符串连接。其中,“[,]”表示字符串连接的分隔符,如果选择使用[over (partition by )]则会使其变成分析函数;
使用注意:
SELECT c.gysid, listagg(c.wzlbid,',') within GROUP (ORDER BY c.wzlbid) FROM wzgl_gys_zrwmfw c GROUP BY gysid
这几个方法都可以实现行转列,达到想要的效果。
但当数据量比较大时却报ORA-01489:字符串连接的结果过长。
select aaa.aaa_id, listagg(aaa.line_id, ',') within GROUP(order by(aaa.line_id)) as ids from aaa group by aaa.aaa_id;
结果
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274 | 354011,354015,354016 |
275 | 355372,355375,355387 |
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 ,'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
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
二、wm_concat(column)
介绍:其函数在Oracle 10g推出,在10g版本中,返回字符串类型,在11g版本中返回clob类型。括号里面的参数是列,而且可以是多个列的集合,也就是说在括号里面可以自由地用‘||’合并字符串。如下面的例子: Select u_id, wmsys.wm_concat(goods || '(' || num || '斤)' ) goods_sum from shopping group by u_id
select aaa.aaa_id, wm_concat(aaa.line_id) as ids from aaa group by aaa.aaa_id;
结果
274 | 354011,354015,354016 |
275 | 355372,355375,355387 |
三、sys_connect_by_path(column,<分隔符>)
介绍:其函数在Oracle 9i 版本中推出,用来合并链路的字符串。注意的是其一定要和connect by子句合用!
第一个参数是形成树形式的字段,第二个参数是父级和其子级分隔显示用的分隔符。