--1 建表
create table city_table
(
city_name varchar2(100)
,District varchar2(100)
);
--2 插入數據
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '東城區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '西城區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '崇文區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '宣武區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '朝陽區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '海淀區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '豐台區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '石景山區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '門頭溝區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '房山區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '通州區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '順義區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '昌平區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '大興區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '懷柔區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '平谷區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '密雲縣');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('北京', '延慶縣');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '河東區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '河西區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '南開區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '河北區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '紅橋區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '塘沽區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '漢沽區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '大港區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '東麗區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '西青區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '北辰區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '津南區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '武清區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '寶坻區');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '靜海縣');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '寧河縣');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '薊縣');
insert into CITY_TABLE (CITY_NAME, DISTRICT)values ('天津', '和平區');
commit;
--進擊吧
select city_name,wm_concat(District||chr(10))
from city_table
group by city_name;
--結果發現，里面的子信息會按照一行一行的方式進行排列(chr(13),chr(10))
chr(9)的作用是空格