db = CITY
Table 1 : parkingzones PK
id_parking
SHAPE

Table 2 : dangerareas DA
id_area
SHAPE

SELECT
 (area_parkings/area_zones*100) as pct_overlap

FROM
(SELECT(SDO_GEOM.SDO_AREA
     (SDO_GEOM.SDO_INTERSECTION(PK.SHAPE,DA.SHAPE,0,05)0,05)) area_parkings
  FROM CITY.parkingzones PK
       CITY.dangerareas DA),
 (SELECT (SDO_GEOM.SDO_AREA(PK.SHAPES,0.05)) area_zones )
  FROM CITY.parkingzones PK);