1.前言

Oracle可用連接函數(shù)會介紹以下幾個

Oracle列轉(zhuǎn)行函數(shù) Listagg()

strcat()

wmsys.wm_concat()

2.Oracle列轉(zhuǎn)行函數(shù) Listagg()

2.1最基礎的用法：

LISTAGG(XXX,XXX) WITHIN GROUP( ORDER BY XXX)

用法就像聚合函數(shù)一樣，通過Group by語句，把每個Group的一個字段，拼接起來。

其中LISTAGG函數(shù)第一個參數(shù)為要拼接的字段,第二個參數(shù)為用什么字符串進行連接

eg : listagg(city,’,’)

后面GROUP()中為對連接之后的行數(shù)據(jù)按什么字段進行排序

eg : order by city

with temp as(

select 'China' nation ,'Guangzhou' city from dual union all

select 'China' nation ,'Shanghai' city from dual union all

select 'China' nation ,'Beijing' city from dual union all

select 'USA' nation ,'New York' city from dual union all

select 'USA' nation ,'Bostom' city from dual union all

select 'Japan' nation ,'Tokyo' city from dual

)

select nation,listagg(city,',') within GROUP (order by city) as Cities

from temp

group by nation

運行結果：

2.2同樣是聚合函數(shù)，還有一個高級用法：

就是over(partition by XXX)

也就是說，在你不實用Group by語句時候，也可以使用LISTAGG函數(shù)：

with temp as(

select 500 population, 'China' nation ,'Guangzhou' city from dual union all

select 1500 population, 'China' nation ,'Shanghai' city from dual union all

select 500 population, 'China' nation ,'Beijing' city from dual union all

select 1000 population, 'USA' nation ,'New York' city from dual union all

select 500 population, 'USA' nation ,'Bostom' city from dual union all

select 500 population, 'Japan' nation ,'Tokyo' city from dual

)

select population,

nation,

city,

listagg(city,',') within GROUP (order by city) over (partition by nation) rank

from temp

運行結果：

2.3總結

listagg()函數(shù)支持最低版本需要Oracle 11gR2,查詢自己Oracle版本sql如下,

SELECT v.VERSION FROM v$instance v;

如果版本低于11g,查詢會報錯 [未找到要求的 FROM 關鍵字]

3.strcat()

with temp as(

select 'China' nation ,'Guangzhou' city from dual union all

select 'China' nation ,'Shanghai' city from dual union all

select 'China' nation ,'Beijing' city from dual union all

select 'USA' nation ,'New York' city from dual union all

select 'USA' nation ,'Bostom' city from dual union all

select 'Japan' nation ,'Tokyo' city from dual

)

select nation,strcat(city) from temp

group by nation

結果為:

注意:如果執(zhí)行報錯,報錯內(nèi)容為 strcat標識符無效,則你的版本缺少這個函數(shù),手動執(zhí)行下面的strcat源碼即可

ORACLE 字符串聚合函數(shù) strCat

create or replace type strcat_type as object

(

currentstr varchar2(4000),

currentseprator varchar2(8),

static function ODCIAggregateInitialize(sctx IN OUT strcat_type) return number,

member function ODCIAggregateIterate(self IN OUT strcat_type,value IN VARCHAR2) return number,

member function ODCIAggregateTerminate(self IN strcat_type,returnValue OUT VARCHAR2, flags IN number) return number,

member function ODCIAggregateMerge(self IN OUT strcat_type,ctx2 IN strcat_type) return number

);

create or replace type body strcat_type is

static function ODCIAggregateInitialize(sctx IN OUT strcat_type) return number is

begin

sctx := strcat_type('',',');

return ODCIConst.Success;

end;

member function ODCIAggregateIterate(self IN OUT strcat_type, value IN VARCHAR2) return number is

begin

if self.currentstr is null then

self.currentstr := value;

else

self.currentstr := self.currentstr ||currentseprator || value;

end if;

return ODCIConst.Success;

end;

member function ODCIAggregateTerminate(self IN strcat_type, returnValue OUT VARCHAR2, flags IN number) return number is

begin

returnValue := self.currentstr;

return ODCIConst.Success;

end;

member function ODCIAggregateMerge(self IN OUT strcat_type, ctx2 IN strcat_type) return number is

begin

if ctx2.currentstr is null then

self.currentstr := self.currentstr;

elsif self.currentstr is null then

self.currentstr := ctx2.currentstr;

else

self.currentstr := self.currentstr || currentseprator || ctx2.currentstr;

end if;

return ODCIConst.Success;

end;

end;

CREATE OR REPLACE FUNCTION strcat (input VARCHAR2) RETURN VARCHAR2 PARALLEL_ENABLE AGGREGATE USING strcat_type;

4.wmsys.wm_concat()

注意:11gr2和12C上已經(jīng)摒棄了wm_concat函數(shù),所以要用連接函數(shù),建議使用之前介紹的兩種.如果之前老項目使用了這個函數(shù),需要重建該函數(shù)或者在當前運行oracle版本中沒有這個函數(shù)請看這?“WM_CONCAT”: 標識符無效

with temp as(

select 1 grp, 'a1' str from dual

union

select 1 grp, 'a2' str from dual

union

select 2 grp, 'b1' str from dual

union

select 2 grp, 'b2' str from dual

union

select 2 grp, 'b3' str from dual

)

select grp, wmsys.wm_concat(str)

from temp

group by grp

總結

以上是生活随笔為你收集整理的oracle的连接函数,Oracle各种连接函数总结的全部內(nèi)容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內(nèi)容還不錯，歡迎將生活随笔推薦給好友。