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

构建测试表：

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;

 

要求输出结果：

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

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

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 

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