十进制       十六进制
88               58

用法一：
Converts a HEX number  to  o FLOAT (转换一个十六进制数的浮标)

SQL> select to_number(58,'xx') from dual;

TO_NUMBER(58,'XX')
------------------
                88
                    
               
用法二：
Converts a HEX number to DECIMA       (一个十六进制转换为十进制)

SQL> SELECT TO_NUMBER(58,'xxxxxxx') FROM dual;

TO_NUMBER(58,'XXXXXXX')
-----------------------
                     88

SQL> SELECT TO_NUMBER(58,'xx') FROM dual;

TO_NUMBER(58,'XX')
------------------
                88

SQL> SELECT TO_NUMBER(58,'x') FROM dual;
SELECT TO_NUMBER(58,'x') FROM dual
                 *
ERROR at line 1:
ORA-01722: invalid number

后面x的位数必须大于等于 前面16进制数字的位数

用法三：
Converts a DECIMA  to HEX number  (十进制转换为十六进制)
SQL> select to_char(88,'xx') from dual;

TO_
---
 58