如何使用 PLSQL 反转数字

Question

我正在尝试编写一个 PLSQL 代码来反转数字

SET SERVEROUTPUT ON;

DECLARE 
   v_num number :=120;
   v_store_values NUMBER;
   v_length NUMBER;
   v_output NUMBER; 
BEGIN
   SELECT LENGTH(v_num) INTO v_length FROM DUAL;
   FOR v_counter IN 1..v_length LOOP
         SELECT SUBSTR(v_num,-(v_counter),v_counter) INTO v_store_values FROM DUAL;
         DBMS_OUTPUT.PUT_LINE(v_store_values);  
   END LOOP;
END;
/

它给了我输出：

0
2
1

但我想要水平输出： 021

Answer 1

你真的不需要 PL/SQL； 考虑

SQL> select listagg(substr('120', -level, 1)) result
  2  from dual
  3  connect by level <= length('120');

RESULT
--------------------------------------------------------------------------------
021

SQL>

---

如果它必须是PL/SQL：

SQL> declare
  2    result varchar2(20);
  3  begin
  4    select listagg(substr('120', -level, 1)) result
  5    into result
  6    from dual
  7    connect by level <= length('120');
  8
  9    dbms_output.put_line(result);
 10  end;
 11  /
021

PL/SQL procedure successfully completed.

SQL>

Answer 2

这行得通吗？ 希望我已经编写了正确的代码，但尚未对其进行测试。

DECLARE
num number;
reverse_num number:=0;

begin
num:=69696;
while num>0
loop
reverse_num:=(reverse_num*10) + mod(num,10);
num:=trunc(num/10);
end loop;

dbms_output.put_line(' Reversed number is : '|| reverse_num);

Answer 3

您可以使用下面的简单REVERSE功能，但请注意它是一个未记录的功能。

select reverse(to_char(120))
from   dual;

或者您可以使用支持的utl_raw.reverse

 select utl_raw.cast_to_varchar2(utl_raw.reverse(utl_raw.cast_to_raw (to_char(120))))
 from   dual;