本文详细介绍了WM_CONCAT函数在Oracle中如何实现行转列的效果，通过多个实例展示了其使用方法，并提供了创建表和插入数据的过程。文章涵盖了基本用法、按ID分组和按ID及名称分组的场景，最后讨论了函数的性能和应用场景。
select t.rank, t.Name from t_menu_item t;
<wbr><wbr><wbr> 10 CLARK<br><wbr><wbr><wbr> 10 KING<br><wbr><wbr><wbr> 10 MILLER<br><wbr><wbr><wbr> 20 ADAMS<br><wbr><wbr><wbr> 20 FORD<br><wbr><wbr><wbr> 20 JONES<br><wbr><wbr><wbr> 20 SCOTT<br><wbr><wbr><wbr> 20 SMITH<br><wbr><wbr><wbr> 30 ALLEN<br><wbr><wbr><wbr> 30 BLAKE<br><wbr><wbr><wbr> 30 JAMES<br><wbr><wbr><wbr> 30 MARTIN<br><wbr><wbr><wbr> 30 TURNER<br><wbr><wbr><wbr> 30 WARD<br>
--------------------------------<br>
我们通过 10g 所提供的 WMSYS.WM_CONCAT 函数即可以完成 行转列的效果<br><wbr><wbr><wbr>select t.rank, WMSYS.WM_CONCAT(t.Name) TIME From t_menu_item t GROUP BY t.rank;<br>
DEPTNO ENAME<br>
------ ----------<br><wbr><wbr><wbr> 10 CLARK, KING, MILLER<br><wbr><wbr><wbr> 20 ADAMS, FORD, JONES, SCOTT, SMITH<br><wbr><wbr><wbr> 30 ALLEN, BLAKE, JAMES, MARTIN, TURNER, WARD</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
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 inserted
SQL> insert into idtable values(20,'mn');
1 row inserted
SQL> select * from idtable;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- ------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 bc<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ij<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6 rows selected
SQL> select id,wmsys.wm_concat(name) name from idtable
2 group by id;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- --------------------------------------------------------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi,ij,mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
SQL> select id,wmsys.wm_concat(name) over (order by id) name from idtable;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- --------------------------------------------------------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi,ij,mn<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi,ij,mn<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi,ij,mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6 rows selected
SQL> select id,wmsys.wm_concat(name) over (order by id,name) name from idtable;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- --------------------------------------------------------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi,ij<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ab,bc,cd,hi,ij,mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
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;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- --------------------------------------------------------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab,bc,cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi,ij,mn<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi,ij,mn<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi,ij,mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6 rows selected
SQL> select id,wmsys.wm_concat(name) over (partition by id,name) name from idtable;
<wbr><wbr><wbr><wbr><wbr><wbr><wbr> ID NAME<br> ---------- --------------------------------------------------------------------------------<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 ab<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 bc<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 10 cd<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 hi<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 ij<br><wbr><wbr><wbr><wbr><wbr><wbr><wbr> 20 mn</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
6 rows selected
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