<xs:group name="lexical_elements"><xs:annotation><xs:documentation xml:lang="en">lexical elements.this group is used for documentation only, not used in XML file.</xs:documentation></xs:annotation><xs:all><xs:element ref="sql_terminal_character"/><xs:element ref="token"/><xs:element ref="separator"/><xs:element ref="literal"/><xs:element ref="identifier"/></xs:all></xs:group>