Need help with OracleDB SQL Developer Regular Expression Query

When I let this Query run in my Oracle SQL Developer 1.5.3

select 
  COLUMNNAME , 
  REPLACE( COLUMNNAME, 'BEFORESTRING', 'AFTERSTRING' ) 
    as COLUMNNAME
from 
  TABLENAME
;

This ain't working. Does anyone know what's wr开发者_StackOverflow社区ong with the Query? Or maybe the Oracle DB Developer Tool has a bug?

Update: I want to change the table not only print out a regex match.

---

Try:

update tablename
set columnname =  REPLACE( COLUMNNAME, 'BEFORESTRING', 'AFTERSTRING' ) ;

That will change all rows unless you add a WHERE clause. If there is a lot of data this would be more efficient:

update tablename
set columnname =  REPLACE( COLUMNNAME, 'BEFORESTRING', 'AFTERSTRING' ) 
where columnname like '%BEFORESTRING%';