This Oracle tutorial explains how to use the Oracle/PLSQL TO_SINGLE_BYTE function.
TO_SINGLE_BYTE(x)
converts the multi-byte characters in x to
the corresponding single-byte characters.
The syntax for the Oracle/PLSQL TO_SINGLE_BYTE function is:
TO_SINGLE_BYTE( char )
char can be a char, varchar2, nchar, or nvarchar2 value.
SQL> select to_single_byte('this is a test') from dual;
TO_SINGLE_BYTE
--------------
this is a test
SQL>