select chr(ascii('b') - 1) "value" from dual
/*
v
-
a

1 row selected.
*/

select chr(ascii('c') - 1) "value" from dual
/*
v
-
b

1 row selected.
*/

select chr(ascii('z') - 1) "value" from dual
/*
v
-
y

1 row selected.
*/

------解决方案--------------------
如果传为A-->前面没字母时怎么显示

------解决方案--------------------
SQL code
查看范围 

select ascii('a'), ascii('z'), ascii('A'), ascii('Z') from dual;

/**
       ASCII('A')    ASCII('Z')    ASCII('A')    ASCII('Z')
1    97    122    65    90

**/

select chr(97), chr(122), chr(65), chr(90) from dual;
/**

       CHR(97)    CHR(122)    CHR(65)    CHR(90)
1    a    z    A    Z

**/

------解决方案--------------------
探讨

如果传为A-->前面没字母时怎么显示


------解决方案--------------------
[code=SQL][/code]create or replace function f_change_alph (v_str in varchar2)  return varchar2 is

v_ret varchar2(2);
begin
  select translate(v_str,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','BCDEFGHIJKLMNOPQRSTUVWXYZA') into v_ret from  dual;
 return v_ret;
end f_change_alph;


--test
select f_change_alph('Z') res from  dual;
A


------解决方案--------------------
[Quote=引用:]
[code=SQL][/code]create or replace function f_change_alph (v_str in varchar2) return varchar2 is

v_ret varchar2(2);
begin
 select translate(v_str,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','BCDEFGHIJKLMNOPQRS……
[/Quote]

+1


------解决方案--------------------
SQL code

--将b当作参数传入
select decode('b','a','z',chr(ascii('b')-1)) as vaule from dual

------解决方案--------------------
可以使用TRANSLATE()函数，轻松实现。
参考代码：

SQL code

SELECT TRANSLATE(原始字符串, 'bcdefghijklmnopqrstuvwxyzaBCDEFGHIJKLMNOPQRSTUVWXYZA',
                              'abcdefghijklmnopqrstuvwxyzaABCDEFGHIJKLMNOPQRSTUVWXYZ');

------解决方案--------------------
translate函数果然牛！！！

------解决方案--------------------
用catch case吧，很好的