Oracle PL/SQL Tutorial/Character String Functions/COMPOSE
compose("de" || unistr("\0300") )
<source lang="sql">
SQL> SQL> SQL> select compose("de" || unistr("\0300") ) from dual; dF 1 row selected. SQL></source>
<source lang="sql">
SQL> SQL> SQL> select compose("de" || unistr("\0300") ) from dual; dF 1 row selected. SQL></source>