oracle wm_concat函数，用于列转行，逗号分隔

wm_concat函数
 
 
 

首先让我们来看看这个神奇的函数wm_concat(列名),该函数可以把列值以","号分隔起来,并显示成一行,接下来上例子,看看这个神奇的函数如何应用
 
准备测试数据
 
 
 
SQL> create table test(id number,name varchar2(20));
 
SQL> insert into test values(1,'a');
 
SQL> insert into test values(1,'b');
 
SQL> insert into test values(1,'c');
 
SQL> insert into test values(2,'d');
 
SQL> insert into test values(2,'e');
 
 
 
SQL> commit;
 
 
 
效果1 : 行转列
 
 
 
SQL> select wm_concat(name) from test;
 
WM_CONCAT(NAME)
 
-------------------------------------------------------------------------
 
a,b,c,d,e
 
 
 
效果2: 把结果里的逗号替换成"|"
 
 
 
SQL> select replace(wm_concat(name),',','|') from test;
 
REPLACE(WM_CONCAT(NAME),',','|')
 
-----------------------------------------------------------------------
 
a|b|c|d|e
 
 
 
 
 
效果3:按ID分组合并name
 
 
 
SQL> select id,wm_concat(name) name from test group by id;
 
ID NAME
 
---------- ------------------------------
 
1 a,b,c
 
2 d,e
 
 
 
懒人扩展用法:
 
案例:我要写一个视图,类似"create or replace view as select 字段1,...字段50 from tablename" ,基表有50多个字段,要是靠手工写太麻烦了,有没有什么简便的方法? 当然有了,看我如果应用wm_concat来让这个需求变简单
 
 
 
SQL> select 'create or replace view as select '|| wm_concat(column_name) || ' from dept'from user_tab_columns where table_name='DEPT';
 
'CREATEORREPLACEVIEWASSELECT'||WM_CONCAT(COLUMN_NAME)||'FROMDEPT'
 
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create or replace view as select DEPTNO,DNAME,LOC from dept