学习一个分组组合查询

分组组合查询在实际应用中有用到，看了网上的一些例子做个记录，仅作为学习记录

首先创建测试表：

create table TABLE1     
(     
  ID   INTEGER,     
  NAME VARCHAR2(10)     
) ;      
create table TABLE2     
(     
  ID   INTEGER,     
  ROLE VARCHAR2(10)     
);     
insert into TABLE1 (ID, NAME) values (1, '张三');     
insert into TABLE1 (ID, NAME) values (2, '李四');     
commit;        
insert into TABLE2 (ID, ROLE) values (1, '查询');     
insert into TABLE2 (ID, ROLE) values (1, '分析');     
insert into TABLE2 (ID, ROLE) values (1, '决策');     
insert into TABLE2 (ID, ROLE) values (2, '查询');
commit ;

1.用函数进行查询

select table1.*, wmsys.wm_concat(role)
   from table1, table2
   where table1.id = table2.id
   group by table1.id, table1.name

2.迭代查询

select id, name, ltrim(max(sys_connect_by_path(role, ',')), ',') from(select row_number() over(partition by table1.id order by name) rn, table1.*, role from table1, table2 where table1.id = table2.id) start
  with rn = 1 connect by prior rn = rn - 1 and prior id = id group by id, name order by id

要是默认用逗号隔开，第一种就行，要是可变字符，用第二种