1 PASSTHRU 2 Expression 2.1? TO DatabaseReference 2.2? VALUES ( 2.2.1+ , 2.2.1 Expression 2.2.2 ) 2 (1) ( Expression 2.1? , 2.1.1+ , 2.1.1 Expression 2.1.2 ) WHERE 1 DatabaseReference = Database . DataSourceClause