oracle 取俩个字符串的差集

思路：

--funcation RemoveSameStr(in_str,splitStr) ;用于去除重复值 ;
 SELECT  b.memberid,  RemoveSameStr(wm_concat(b.productidlist),',') AS productidlist
  FROM BASE_ACCOUNT_BILL_GROUP  b
  WHERE  b.grouptype =3
  GROUP BY  b.memberid ;

2.创建 FUNCTION REMOVESAMESTR(OLDSTR VARCHAR2, SIGN VARCHAR2);

 CREATE OR REPLACE FUNCTION REMOVESAMESTR(OLDSTR VARCHAR2, SIGN VARCHAR2)
   RETURN VARCHAR2 IS
   STR          VARCHAR2(1000);
   CURRENTINDEX NUMBER;
   STARTINDEX   NUMBER;
   ENDINDEX     NUMBER;

   TYPE STR_TYPE IS TABLE OF VARCHAR2(30) INDEX BY BINARY_INTEGER;
   ARR STR_TYPE;

   RESULT VARCHAR2(1000);
 BEGIN
   -- 空字符串
   IF OLDSTR IS NULL THEN
     RETURN('');
   END IF;
   --字符串太长
   IF LENGTH(OLDSTR) > 1000 THEN
     RETURN(OLDSTR);
   END IF;
   STR := OLDSTR;

   CURRENTINDEX := 0;
   STARTINDEX   := 0;

   LOOP
     CURRENTINDEX := CURRENTINDEX + 1;
     ENDINDEX     := INSTR(STR, SIGN, 1, CURRENTINDEX);
     IF (ENDINDEX <= 0) THEN
       EXIT;
     END IF;

     ARR(CURRENTINDEX) := TRIM(SUBSTR(STR,
                                      STARTINDEX + 1,
                                      ENDINDEX - STARTINDEX - 1));
     STARTINDEX := ENDINDEX;
   END LOOP;

   --取最后一个字符串:
   ARR(CURRENTINDEX) := SUBSTR(STR, STARTINDEX + 1, LENGTH(STR));

   --去掉重复出现的字符串:
   FOR I IN 1 .. CURRENTINDEX - 1 LOOP
     FOR J IN I + 1 .. CURRENTINDEX LOOP
       IF ARR(I) = ARR(J) THEN
         ARR(J) := '';
       END IF;
     END LOOP;
   END LOOP;

   STR := '';
   FOR I IN 1 .. CURRENTINDEX LOOP
     IF ARR(I) IS NOT NULL THEN
       STR := STR || SIGN || ARR(I);
       --数组置空:
       ARR(I) := '';
     END IF;
   END LOOP;
   --去掉前面的标识符:
   RESULT := SUBSTR(STR, 2, LENGTH(STR));
   RETURN(RESULT);
 END REMOVESAMESTR;

3.创建 Function COMPARETWOSTR(IN_STR IN VARCHAR2) ；

 CREATE OR REPLACE FUNCTION COMPARETWOSTR(IN_STR IN VARCHAR2)
   RETURN VARCHAR2 AS
   RESULTSTR VARCHAR2(4000);
 BEGIN
   SELECT LISTAGG(STR, ',') WITHIN GROUP(ORDER BY STR)
     INTO RESULTSTR
     FROM (SELECT LEVEL STR
             FROM DUAL
           CONNECT BY LEVEL <= 17
           MINUS
           SELECT TO_NUMBER(COLUMN_VALUE) STR
             FROM TABLE(SPLITSTR(IN_STR, ',')));
   RETURN RESULTSTR;
 EXCEPTION
   WHEN OTHERS THEN
     DBMS_OUTPUT.PUT_LINE(SQLCODE || SQLERRM ||
                          DBMS_UTILITY.FORMAT_ERROR_BACKTRACE);
 END COMPARETWOSTR;

4.创建 function splitstr(p_string IN VARCHAR2, p_delimiter IN VARCHAR2) RETURN str_split ；

CREATE OR REPLACE TYPE "STR_SPLIT"   IS TABLE OF VARCHAR2 (4000)；

 CREATE OR REPLACE FUNCTION splitstr(p_string IN VARCHAR2, p_delimiter IN VARCHAR2)
    /**********************************************************************
     * xdshi add blockment 2015-09-21
     * 通用方法：按列返回分割字符串后的内容
     * 入参：p_string 分割字符串
     *       p_delimiter 分割符
     * 返回：每个分割出来的字符串
     **********************************************************************/
     RETURN str_split
     PIPELINED
 AS
     v_length   NUMBER := LENGTH(p_string);
     v_start    NUMBER := 1;
     v_index    NUMBER;
 BEGIN
     WHILE(v_start <= v_length)
     LOOP
         v_index := INSTR(p_string, p_delimiter, v_start);

         IF v_index = 0
         THEN
             PIPE ROW(SUBSTR(p_string, v_start));
             v_start := v_length + 1;
         ELSE
             PIPE ROW(SUBSTR(p_string, v_start, v_index - v_start));
             v_start := v_index + 1;
         END IF;
     END LOOP;

     RETURN;
 END splitstr;

5.最终结果