在Oracle常用的数据处理中，会遇到将某个字符串倒序输出的需求，查询了下，Oracle中没有特别的函数来实现该功能，下面将利用其自带Substr函数的截取字符功能，通过自定义函数来实现字符串倒序输出的处理。

create or replace function fun_str_dx_test1(str in varchar2)

return varchar2

is

result_str varchar2(3000);

str_len int;

i int;

str_tmp varchar2(3000);

begin

  select length(str) into str_len from dual;

  for i in 0..str_len-1 loop

    select substr(str,str_len-i,1) into str_tmp from dual;

    result_str:=result_str||str_tmp;

end loop;

return(result_str);

end fun_str_dx_test1;

create or replace function fun_str_dx_test2(str in varchar2) 

return varchar2 

is

Result varchar2(5000);

str_len int;

i int;

str1 varchar2(5000);

str2 varchar2(5000);

begin

select length(str) into str_len from dual;

str1 := str;

for i in 1 .. str_len loop

select substr(str1, -1) into str2 from dual;

result := result || str2;

select substr(str1, 1, str_len - i) into str1 from dual;

end loop;

return(result);

end fun_str_dx_test2;

本文主要参考网上的各种写法，后经总结，通过实例测试而来。