1、两个字段表，id和name，其中id和name一对多关系，需要列转行操作：
create table test(id number, name varchar2(20));
insert into test values(1, 'a');
insert into test values(2, 'b');--添加多条数据，一对多
select tmp.id,
max(decode(tmp.row_number, 1, name)) as c1,
max(decode(tmp.row_number, 2, name)) as c2,
max(decode(tmp.row_number, 3, name)) as c3,
max(decode(tmp.row_number, 4, name)) as c4,
max(decode(tmp.row_number, 5, name)) as c5
from (select t.*, row_number() over(partition by t.id order by name) as row_number from test t) tmp
group by tmp.id
缺点：1对n，需要添加n个max行，少量的统计可以这样做。
2、行转列，将n个字段通过字符连接成一个字段进行展示：
oracle 12g通过listagg函数实现，可自行百度。
