替代Oracle函數wmsys_wm_concat()函數

create or replace function postgresql(p_tname varchar2, p_colname varchar2)
return clob is

v_tmp    varchar2(200);
v_result clob;
v_cum    sys_refcursor;
begin

open v_cum for 'select ' || p_colname || ' from ' || p_tname;
loop
    fetch v_cum
      into v_tmp;
    exit when v_cum%notfound;
    v_result := v_result || v_tmp;
end loop;
dbms_output.put_line(v_result);
return v_result;
end;

select postgresql('emp','ename') from dual

2.sys_connect_by_path

3.create or replace TYPE zh_concat_im
AUTHID CURRENT_USER AS OBJECT
(
   CURR_STR VARCHAR2(32767),
   STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im) RETURN NUMBER,
   MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,
            P1 IN VARCHAR2) RETURN NUMBER,
   MEMBER FUNCTION ODCIAGGREGATETERMINATE(SELF IN zh_concat_im,
                              RETURNVALUE OUT VARCHAR2,
                              FLAGS IN NUMBER)
                  RETURN NUMBER,
   MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT zh_concat_im,
                   SCTX2 IN   zh_concat_im) RETURN NUMBER
);
/

create or replace TYPE BODY zh_concat_im
IS
   STATIC FUNCTION ODCIAGGREGATEINITIALIZE(SCTX IN OUT zh_concat_im)
   RETURN NUMBER
   IS
   BEGIN
SCTX := zh_concat_im(NULL) ;
RETURN ODCICONST.SUCCESS;
   END;
   MEMBER FUNCTION ODCIAGGREGATEITERATE(SELF IN OUT zh_concat_im,
      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 zh_concat_im,
                              RETURNVALUE OUT VARCHAR2,
                              FLAGS IN NUMBER)
RETURN NUMBER
   IS
   BEGIN
RETURNVALUE := CURR_STR ;
RETURN ODCICONST.SUCCESS;
   END;
   MEMBER FUNCTION ODCIAGGREGATEMERGE(SELF IN OUT zh_concat_im,
                                  SCTX2 IN zh_concat_im)
   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;
/

函數：
create or replace FUNCTION zh_concat(P1 VARCHAR2)
RETURN VARCHAR2 AGGREGATE USING zh_concat_im ;

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