value_spec 
<
value_spec> ::=
<literal>
| <parameter_spec>
| NULL
| USER
| USERGROUP
| LOCALSYSDBA
| SYSDBA [(<user_name>)]
| SYSDBA [(<usergroup_name>)]
| [<owner>.]<sequence_name>.NEXTVAL
| [<owner>.]<sequence_name>.CURRVAL
| DATE
| TIME
| TIMESTAMP
| TIMEZONE
| TRUE
| FALSE
| TRANSACTION
| UTCDIFF