If you Googled
ORA-00904
and followed the first link, you would have seen this:
ORA-00904: string: invalid identifier
Cause: The column name entered is either missing or invalid.
Action: Enter a valid column name. A valid column name must
begin with a letter, be less than or equal to 30
characters, and consist of only alphanumeric characters
and the special characters $, _, and #. If it
contains other characters, then it must be enclosed
in double quotation marks. It may not be a
reserved word.
If you saw the last sentence "It may not be a reserved word", then you would have Googled "Oracle reserved words", and on the first link you would have seen that
both role and online are reserved words.