Oracle函数wmsys.wm_concat的使用

首先介绍语法：

wmsys.wm_concat

Definition:

The Oracle PL/SQL WM_CONCAT function is used to aggregate data from a number of rows into a single row, giving a list of data associated with a specific value. In effect, it cross-tabulates a comma delimited list.

  www.2cto.com 

Note that WM_CONCAT is undocumented and unsupported by Oracle, meaning it should not be used in production systems. The LISTAGG function, which can produce the same output asWM_CONCAT is both documented and supported by Oracle.

例子：

[sql]

select t1.main_id, 

       to_char( wmsys.wm_concat(t1.send_id || '||' || t2.realname || '||' || 

                               t2.IMG_PATH)) sendidlist 

  from LCMS_SEND_USER t1, LCMS_USER_STUD t2 

group by t1.main_id; 

结果：

网络中也有这样使用：

下面只是收藏：

[sql]

SQL> select id, wmsys.wm_concat(name) over (order by id) name from idtable; 

    www.2cto.com 

        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]

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 

    www.2cto.com 

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; 

    www.2cto.com 

        ID NAME 

---------- -------------------------------------------------------------------------------- 

        10 ab 

        10 bc 

        10 cd 

        20 hi 

        20 ij 

        20 mn 

 

6 rows selected