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Oracle9i增添 wm_concat函数(转)

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Oracle9i添加 wm_concat函数(转)

一：

创建type头

create or replace type string_sum_obj as object (

--聚合函数的实质就是一个对象

sum_string varchar2(4000),

static function ODCIAggregateInitialize(v_self in out string_sum_obj) return number,

--对象初始化

member function ODCIAggregateIterate(self in out string_sum_obj, value in varchar2) return number,

--聚合函数的迭代方法(这是最重要的方法)

member function ODCIAggregateMerge(self in out string_sum_obj, v_next in string_sum_obj) return number,

--当查询语句并行运行时,才会使用该方法,可将多个并行运行的查询结果聚合

member function ODCIAggregateTerminate(self in string_sum_obj, return_value out varchar2 ,v_flags in number) return number

--终止聚集函数的处理,返回聚集函数处理的结果.

)

创建type具体

create or replace type body string_sum_obj is

static function ODCIAggregateInitialize(v_self in out string_sum_obj) return number is

begin

v_self := string_sum_obj(null);

return ODCICONST.Success;

end;

member function ODCIAggregateIterate(self in out string_sum_obj, value in varchar2) return number is

begin

/* 连接，解决逗号分隔第一个字母是逗号的问题 */

if not self.sum_string is null then

self.sum_string := self.sum_string ||','|| value;

else

self.sum_string := self.sum_string || value;

end if;

return ODCICONST.Success;

/* 最大值 */

if self.sum_string

self.sum_string:=value;

end if;

/* 最小值 */

if self.sum_string>value then

self.sum_string:=value;

end if;

return ODCICONST.Success;

end;

member function ODCIAggregateMerge(self in out string_sum_obj, v_next in string_sum_obj) return number is

begin

/* 连接 */

self.sum_string := self.sum_string || v_next.sum_string;

return ODCICONST.Success;

/* 最大值 */

if self.sum_string

self.sum_string:=v_next.sum_string;

end if;

/* 最小值 */

if self.sum_string>v_next.sum_string then

self.sum_string:=v_next.sum_string;

end if;

return ODCICONST.Success;

end;

member function ODCIAggregateTerminate(self in string_sum_obj, return_value out varchar2 ,v_flags in number) return number is

begin

return_value:= self.sum_string;

return ODCICONST.Success;

end;

end;

创建函数

create or replace function wm_concat(value Varchar2) return Varchar2

parallel_enable aggregate using string_sum_obj;

二：

先创建这个类型

create or replace type strcat_type as object (

cat_string varchar2(4000),

static function ODCIAggregateInitialize(cs_ctx In Out strcat_type) return number,

member function ODCIAggregateIterate(self In Out strcat_type,value 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

)

缺少类型体内容：

....

然后创建这个函数

CREATE OR REPLACE FUNCTION strcat(input varchar2 )

RETURN varchar2

PARALLEL_ENABLE AGGREGATE USING strcat_type;

几个用法：

9i: SYS_CONNECT_BY_PATH 函数

SQL> select id, replace(wmsys.wm_concat(rmak), ',', '') from test group by id;

ID REPLACE(WMSYS.WM_CONCAT(RMAK),

---------- --------------------------------------------

9 timggg

21 littlefff

23 tom

SQL> select * from idtable;

ID NAME

---------- ------------------------------

10 ab

10 bc

10 cd

20 hi

20 ij

20 mn

6 rows selected

SQL> select id,wmsys.wm_concat(name) name from idtable

2  group by id;

ID NAME

---------- --------------------------------------------

10 ab,bc,cd

20 hi,ij,mn

SQL> select id,wmsys.wm_concat(name) over (order by id) name from idtable;

ID NAME

---------- --------------------------------------------

10 ab,bc,cd

10 ab,bc,cd

10 ab,bc,cd

20 ab,bc,cd,hi,ij,mn

20 ab,bc,cd,hi,ij,mn

20 ab,bc,cd,hi,ij,mn

6 rows selected

SQL> select id,wmsys.wm_concat(name) over (order by id,name) name from idtable;

ID NAME

---------- --------------------------------------------

10 ab

10 ab,bc

10 ab,bc,cd

20 ab,bc,cd,hi

20 ab,bc,cd,hi,ij

20 ab,bc,cd,hi,ij,mn

6 rows selected

个人觉得这个用法比较有趣.

SQL> select id,wmsys.wm_concat(name) over (partition by id) name from idtable;

ID NAME

---------- --------------------------------------------

10 ab,bc,cd

10 ab,bc,cd

10 ab,bc,cd

20 hi,ij,mn

20 hi,ij,mn

20 hi,ij,mn

6 rows selected

SQL> select id,wmsys.wm_concat(name) over (partition by id,name) name from idtable;

ID NAME

---------- --------------------------------------------

10 ab

10 bc

10 cd

20 hi

20 ij

20 mn

6 rows selected

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