| C1 | C2 |
|---|---|
| 1 | C |
| 1 | B |
| 1 | A |
| 2 | A |
| 3 | A |
| 3 | C |
| C1 | LinkedText |
|---|---|
| 1 | C;A;B |
| 2 | A |
| 3 | A;C |
方法一：利用CONNECT BY 實現
SELECT DISTINCT C1,FIRST_VALUE(LTRIM(TEXT, ';')) OVER(PARTITION BY C1 ORDER BY LVL DESC) LinkedText
FROM (SELECT C1, C2, LEVEL AS LVL, SYS_CONNECT_BY_PATH(C2, ';') AS TEXT
FROM (SELECT C1,
C2,
ROW_NUMBER() OVER(PARTITION BY T1.C1 ORDER BY T1.C1) X
FROM T1
ORDER BY T1.C1) T2
CONNECT BY C1 = PRIOR C1
AND X - 1 = PRIOR X) T3
ORDER BY C1
方法二：自定義 聚合函數
1）定義 strcat_type 對象：
create or replace type strcat_type as object
(
-- Author : ADMINISTRATOR
-- Created : 2013-8-7 23:49:51
-- Purpose : String concatenation
-- Attributes
cat_string varchar2(4000),
separator varchar2(1),
-- Member functions and procedures
static function ODCIAggregateInitialize(actx In Out strcat_type) return number,
member function ODCIAggregateIterate(self In Out strcat_type,val in varchar2) return number,
member function ODCIAggregateMerge(self In Out strcat_type,ctx2 In Out strcat_type) return number,
member function ODCIAggregateTerminate(self In Out strcat_type,returnValue Out varchar2,flags in number) return number
)
2）實現 strcat_type 包體：
create or replace type body strcat_type is
-- Member procedures and functions
static function ODCIAggregateInitialize(actx IN OUT strcat_type) return number
is
begin
actx := strcat_type(cat_string => null, separator => ';');
return ODCIConst.Success;
end;
member function ODCIAggregateIterate(self IN OUT strcat_type, val IN varchar2 ) return number
is
begin
self.cat_string := self.cat_string || self.separator || val;
return ODCIConst.Success;
end;
member function ODCIAggregateTerminate(self IN Out strcat_type, returnValue OUT varchar2, flags IN number) return number
is
begin
returnValue := ltrim(rtrim(self.cat_string,self.separator),self.separator);
return ODCIConst.Success;
end;
member function ODCIAggregateMerge(self IN OUT strcat_type, ctx2 IN Out strcat_type) return number
is
begin
self.cat_string := self.cat_string || self.separator || ctx2.cat_string;
return ODCIConst.Success;
end;
end;
3）創建函數
CREATE OR REPLACE FUNCTION strcat(input varchar2) RETURN varchar2
PARALLEL_ENABLE AGGREGATE USING strcat_type;
4）示例
SELECT C1, STRCAT(C2) AS LINKEDTEXT FROM T1 T GROUP BY C1