zoukankan      html  css  js  c++  java
  • wm_concat

    wm_concat(列名),该函数可以把列值以","号分隔起来,并显示成一行


    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'
    --------------------------------------------------------------------------------
    create or replace view as select DEPTNO,DNAME,LOC from dept

  • 相关阅读:
    jmeter如何连接数据库
    jmeter基础之录制篇
    php解压缩
    composer基本使用
    react组件之间的参数传递
    解决VMware Workstation 不可恢复错误: (vcpu-0)
    虚拟机vmware11装Mac ox 10.8 解决windows8.1下unlocker202 vmxsmc.exe已停止工作的问题
    Photoshop学习:打开PS之前需要...
    汇编语言之启航
    Markdown语法介绍
  • 原文地址:https://www.cnblogs.com/q1092813103/p/9023070.html
Copyright © 2011-2022 走看看