First of all, your query does not do what you say it does: it actually returns the nearest building called "Motel" from any of your hydrants. To do what you want (i.e. the opposite) you need to reverse the order of the arguments to SDO_NN: all spatial operators search the first argument, using the value of the second argument.
Then the insert into your HYDRANTS table is wrong:
Insert into hydrants (name,POINT) values ('p57',MDSYS.SDO_POINT_TYPE(589,448,0));
The SDO_POINT_TYPE object is not designed to be used that way: it is only used inside the SDO_GEOMETRY type. The proper way is this:
insert into hydrants (name,POINT) values ('p57',sdo_geometry(2001, null, SDO_POINT_TYPE(589,448,null), null, null));
And of course you need to change your table definition accordingly.
Then your building is also incorrectly created: a polygon must always close, i.e. the last point must be the same as the first point. So the proper shape should be like this:
insert into buildings (NAME,SHAPE) values ('Motel', SDO_GEOMETRY(2003,NULL,NULL,SDO_ELEM_INFO_ARRAY(1,1003,1),SDO_ORDINATE_ARRAY(564,425,585,436,573,458,552,447,564,425)));
Here is the full example:
Create the tables:
create table buildings (
name varchar2(40) primary key,
shape sdo_geometry
);
create table hydrants(
name varchar2(10) primary key,
point sdo_geometry
);
Populate the tables:
insert into buildings (NAME,SHAPE) values ('Motel', SDO_GEOMETRY(2003,NULL,NULL,SDO_ELEM_INFO_ARRAY(1,1003,1),SDO_ORDINATE_ARRAY(564,425,585,436,573,458,552,447,564,425)));
insert into hydrants (name,POINT) values ('p57',sdo_geometry(2001, null, SDO_POINT_TYPE(589,448,null), null, null));
commit;
Confirm that the geometries are all correct:
select name, sdo_geom.validate_geometry_with_context (point, 0.05) from hydrants;
select name, sdo_geom.validate_geometry_with_context (shape, 0.05) from buildings;
Setup spatial metadata and create spatial indexes:
insert into user_sdo_geom_metadata (table_name, column_name, diminfo, srid)
values (
'BUILDINGS',
'SHAPE',
sdo_dim_array (
sdo_dim_element ('X', 0,1000,0.05),
sdo_dim_element ('Y', 0,1000,0.05)
),
null
);
commit;
create index buildings_sx on buildings (shape)
indextype is mdsys.spatial_index;
insert into user_sdo_geom_metadata (table_name, column_name, diminfo, srid)
values (
'HYDRANTS',
'POINT',
sdo_dim_array (
sdo_dim_element ('X', 0,1000,0.05),
sdo_dim_element ('Y', 0,1000,0.05)
),
null
);
commit;
create index hydrants_sx on hydrants (point)
indextype is mdsys.spatial_index;
Now Try the properly written query:
select h.name, h.point.sdo_point.x as x, h.point.sdo_point.y as y
from buildings b, hydrants h
where b.name ='Motel'
and sdo_nn(h.point, b.shape, 'sdo_num_res=1')= 'TRUE';
which returns:
NAME X Y
---------------- ---------- ----------
p57 589 448
1 row selected.