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<value then
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<v_next.sum_string then
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;


[b]几个用法：[/b]

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