Use translate function in update statement
SQL> SQL> create table nchar_samples( 2 char_data char(100), 3 nchar_data nchar(100) 4 ) 5 / Table created. SQL> SQL> insert into nchar_samples( nchar_data ) 2 values ( N'Some text' ) 3 / 1 row created. SQL> SQL> update nchar_samples 2 set char_data = translate( nchar_data using char_cs ) 3 / 1 row updated. SQL> SQL> drop table nchar_samples; Table dropped. SQL> SQL> --