Syntax
<value_spec> ::= <literal> | <parameter_spec> | NULL | USER | USERGROUP | SYSDBA | CURRENT_SCHEMA | UID | [<schema_name>.]<sequence_name>.NEXTVAL | [<schema_name>.]<sequence_name>.CURRVAL | <table_name>.CURRVAL | DATE | TIME | TIMESTAMP | UTCDATE | TIMEZONE | UTCDIFF | TRUE | FALSE | TRANSACTION