wm_concat函式 用法
阿新 • • 發佈:2019-02-16
首先讓我們來看看這個神奇的函式wm_concat(列名),該函式可以把列值以","號分隔起來,並顯示成一行,接下來上例子,看看這個神奇的函式如何應用 準備測試資料 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 : 行轉列 SQL> select wm_concat(name) from test; WM_CONCAT(NAME) ------------------------------------------------------------------------- a,b,c,d,e 效果2: 把結果裡的逗號替換成"|" SQL> select replace(wm_concat(name),',','|') from test; REPLACE(WM_CONCAT(NAME),',','|') ----------------------------------------------------------------------- a|b|c|d|e 效果3:按ID分組合並name SQL> select id,wm_concat(name) name from test group by id; ID NAME ---------- ------------------------------ 1 a,b,c 2 d,e 懶人擴充套件用法: 案例:我要寫一個檢視,類似"create or replace view as select 欄位1,...欄位50 from tablename" ,基表有50多個欄位,要是靠手工寫太麻煩了,有沒有什麼簡便的方法? 當然有了,看我如果應用wm_concat來讓這個需求變簡單 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