Oracle: wmsys.wm_concat、sys_connect_by_path、自定义函数实现行列转换

构建测试表：
Sql代码
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;

要求输出结果：
Sql代码
ID  NAME    ROLE
1    张三 查询,分析,决策
2    李四 查询

方法一、使用wmsys.wm_concat
Sql代码
select table1.*,wmsys.wm_concat(role) from table1,table2 where table1.id=table2.id
group by table1.id,table1.name

方法二、使用sys_connect_by_path
Sql代码
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

方法三、使用自定义函数
Sql代码
create or replace function my_concat(mid in integer) return varchar2       --记住：参数和返回值里的数据类型都不用定义长度
is
result varchar2(4000);    --定义变量，记住Oracle中定义变量不需要
begin
for temp_cursor in (select role from table2 where id=mid) loop     --此处在游标FOR循环中使用查询
result :=result || temp_cursor.role || ',';    --Oracle中字符连接使用||，而sql server中用+
end loop;
result := rtrim(result,',');  --去掉最后一个空格,还有Oracle中的赋值前面没有set
return result;
end;

select table1.*,my_concat(table1.id) from table1,table2 where table1.id=table2.id
group by table1.id,table1.name
order by table1.id