Oracle字符串截取和拼接应用

declare
    targetstr varchar2(2000);
    strlength number;
    position number;
    maxposition number;
    retrunstr varchar2(2000);
    tempstr varchar2(2000);
    endstr number;
begin
    targetstr := '1788987565327、768374872394903、21437238740213483874629、23412341234252345';
    maxposition := 0;
    select LENGTH(targetstr) into strlength  from dual;
    for i in 1..strlength loop
        select instr(str,'、',1,i) into position from （select targetstr as str from dual）;
        --dbms_output.PUT_LINE(position);
        if position > 0 then 
            if maxposition = 0 then 
                select substr(str,0,instr(str,'、',1,1)-1) into retrunstr from （select targetstr as str from dual）;
                select TO_NUMBER(substr(restr,-1)) into endstr from （select retrunstr as restr from dual）;
                if endstr = 3 or endstr = 5 or endstr = 7 then
                    endstr := endstr + 1;
                elsif endstr = 9 then
                    endstr := 0;
                end if;
                select substr(str,0,instr(str,'、',1,1)-2)||TO_CHAR(endstr) into retrunstr from （select targetstr as str from dual）;
            elsif maxposition < position then
                select substr(str,instr(str,'、',1,i-1)+1,instr(str,'、',1,i)-instr(str,'、',1,i-1)-1) into tempstr from （select targetstr as str from dual）;
                select TO_NUMBER(substr(restr,-1)) into endstr from （select tempstr as restr from dual）;
                if endstr = 3 or endstr = 5 or endstr = 7 then
                    endstr := endstr + 1;
                elsif endstr = 9 then
                    endstr := 0;
                end if;
                select substr(str,1,length(str)-1) ||TO_CHAR(endstr) into tempstr from （select tempstr as str from dual）;
                retrunstr := retrunstr || '、'|| tempstr;             
            end if;
            maxposition := position;
        else
            if maxposition > position then
                --特别处理最后一段
                tempstr := '';
                select substr(str,maxposition-length(str)) into tempstr from （select targetstr as str from dual）;
                select TO_NUMBER(substr(restr,-1)) into endstr from （select tempstr as restr from dual）;
                if endstr = 3 or endstr = 5 or endstr = 7 then
                    endstr := endstr + 1;
                elsif endstr = 9 then
                    endstr := 0;
                end if;
                select substr(str,1,length(str)-1) ||TO_CHAR(endstr) into tempstr from （select tempstr as str from dual）;
                retrunstr := retrunstr || '、'|| tempstr;
            end if;
            exit;
        end if;
    end loop;
    dbms_output.PUT_LINE(retrunstr);
end;