oracle wmsys.wm_concat 函数，它的作用是以','链接字符。
例子如下：
SQL> create table idtable (id number,name varchar2(30));
Table created
SQL> insert into idtable values(10,'ab');
1 row inserted
SQL> insert into idtable values(10,'bc');
1 row inserted
SQL> insert into idtable values(10,'cd');
1 row inserted
SQL> insert into idtable values(20,'hi');
1 row inserted
SQL> insert into idtable values(20,'ij');
1 row insertedSQL> insert into idtable values(20,'mn');
1 row inserted
SQL> select * from idtable;
ID NAME---------- ------------------------------ 10 ab 10 bc 10 cd 20 hi 20 ij 20 mn
6 rows selectedSQL> select id,wmsys.wm_concat(name) name from idtable 2 group by id;
ID NAME---------- -------------------------------------------------------------------------------- 10 ab,bc,cd 20 hi,ij,mn
SQL> select id,wmsys.wm_concat(name) over (order by id) name from idtable;
ID NAME---------- -------------------------------------------------------------------------------- 10 ab,bc,cd 10 ab,bc,cd 10 ab,bc,cd 20 ab,bc,cd,hi,ij,mn 20 ab,bc,cd,hi,ij,mn 20 ab,bc,cd,hi,ij,mn
6 rows selected
SQL> select id,wmsys.wm_concat(name) over (order by id,name) name from idtable;
ID NAME---------- -------------------------------------------------------------------------------- 10 ab 10 ab,bc 10 ab,bc,cd 20 ab,bc,cd,hi 20 ab,bc,cd,hi,ij 20 ab,bc,cd,hi,ij,mn
6 rows selected
个人觉得这个用法比较有趣.
SQL> select id,wmsys.wm_concat(name) over (partition by id) name from idtable;
ID NAME---------- -------------------------------------------------------------------------------- 10 ab,bc,cd 10 ab,bc,cd 10 ab,bc,cd 20 hi,ij,mn 20 hi,ij,mn 20 hi,ij,mn
6 rows selected
SQL> select id,wmsys.wm_concat(name) over (partition by id,name) name from idtable;
ID NAME---------- -------------------------------------------------------------------------------- 10 ab 10 bc 10 cd 20 hi 20 ij 20 mn
6 rows selected
转载于:https://www.cnblogs.com/leonsky/archive/2012/09/26/2703539.html
相关资源：Oracle 11g 重建WMSYS.WM_CONCAT函数