select count(1) from Tt_Device_Point point full join tt_area area on point.AREA_ID in (SELECT area_id FROM Tt_Area t START WITH t.area_id = point.AREA_ID CONNECT BY t.tt__area_id = PRIOR t.area_id);
需求是统计所有区域对应的设备总数
------解决方案--------------------
PRIOR t.tt__area_id = t.area_id