Q：oracle19c 如何重建vm_concat函数

没有wm_concat是因为oracle12c数据库中废弃了wm_concat函数

• 第一步 定义对象类型

CREATE OR REPLACE TYPE wmsys.WM_CONCAT_IMPL AS OBJECT
(
CURR_STR VARCHAR2(32767),
STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT WM_CONCAT_IMPL) RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT WM_CONCAT_IMPL,
P1 IN VARCHAR2) RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN WM_CONCAT_IMPL,
RETURNVALUE OUT VARCHAR2,
FLAGS IN NUMBER)
RETURN NUMBER,
MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT WM_CONCAT_IMPL,
SCTX2 IN WM_CONCAT_IMPL) RETURN NUMBER
);
/

• 第二步 定义类型body:  

CREATE OR REPLACE TYPE BODY wmsys.WM_CONCAT_IMPL  
IS  
STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT WM_CONCAT_IMPL)  
RETURN NUMBER  
IS  
BEGIN  
SCTX := WM_CONCAT_IMPL(NULL) ;  
RETURN ODCICONST.SUCCESS;  
END;  
MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT WM_CONCAT_IMPL,  
P1 IN VARCHAR2)  
RETURN NUMBER  
IS  
BEGIN  
IF(CURR_STR IS NOT NULL) THEN  
CURR_STR := CURR_STR || ',' || P1;  
ELSE  
CURR_STR := P1;  
END IF;  
RETURN ODCICONST.SUCCESS;  
END;  
MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN WM_CONCAT_IMPL,  
RETURNVALUE OUT VARCHAR2,  
FLAGS IN NUMBER)  
RETURN NUMBER  
IS  
BEGIN  
RETURNVALUE := CURR_STR ;  
RETURN ODCICONST.SUCCESS;  
END;  
MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT WM_CONCAT_IMPL,  
SCTX2 IN WM_CONCAT_IMPL)  
RETURN NUMBER  
IS  
BEGIN  
IF(SCTX2.CURR_STR IS NOT NULL) THEN  
SELF.CURR_STR := SELF.CURR_STR || ',' || SCTX2.CURR_STR ;  
END IF;  
RETURN ODCICONST.SUCCESS;  
END;  
END;  
/  

• 第三步 自定义行变列函数: 

CREATE OR REPLACE FUNCTION wmsys.wm_concat(P1 VARCHAR2)
RETURN VARCHAR2 AGGREGATE USING wmsys.WM_CONCAT_IMPL ;
/

• 第四步 给其创建同义词及授权，以供其他用户能正常使用。 

create public synonym WM_CONCAT_IMPL for wmsys.WM_CONCAT_IMPL;
create public synonym wm_concat for wmsys.wm_concat;
grant execute on WM_CONCAT_IMPL to public;
grant execute on wm_concat to public;