Hope I am much clearer now.
No not really.

If you just want to update a column,
then use the update with the replace function.

Code:
update SUSERIDTABLE
   set key=replace(key, 'this', 'that')
 where username like '%theother%';
If you want to generate new rows,
then do an insert from a select.

Code:
insert into SUSERIDTABLE ( username )
select 'test'||rownum||'.IsUser'
  from user_objects
 WHERE rownum < 101;