Object Relational Model Spatial Queries - PowerPoint PPT Presentation

Spatial LayerData

Secondary

Filter

Spatial

Functions

Primary

Filter

Spatial Index

Reduced

Data Set

Table where

coordinates are

stored

Index retrieves area of interest (window)

Procedures

that determine

exact relationship

Exact

Result

Set

• Spatial operators:
• Take advantage of spatial indexes
• Require that spatial index exists on the first geometry specified in the operator.
• Spatial Functions:
• Do not take advantage of spatial indexes
• Could be used on small tables that are not spatially indexed

Performs a primary and secondary filter

SDO_WITHIN_DISTANCE

Gets all geometries that are within some distance from a selected geometry

SDO_NN

Gets the ‘n’ closest geometries

SDO_GEOM.RELATE

To determine the relationship between two geometries

To perform a spatial query without using a spatial index (I.e. on a small table)

SDO_GEOM.WITHIN_DISTANCE

Generates a buffer around a geometry and performs a secondary filter

Operators

Functions

boolean := SDO_RELATE

( <geometry-1>,

<geometry-2>,

‘MASK=<mask>

QUERYTYPE=<querytype>

[other optional parameters]’

)

• Performs an exact query (primary and secondary filter)
• Returns TRUE or FALSE

• GEOMETRY-1
• A column of type SDO_GEOMETRY
• GEOMETRY-2
• Variable or column of type SDO_GEOMETRY
• MASK
• Identify spatial relationship to test
• QUERYTYPE
• Valid values are JOIN or WINDOW

Topological relationships

B

A

A

A

B

B

B Inside A

A Contains B

B Covered by A

A Covers B

Touch

A

A

A red

B green

B

B

Overlap

Boundaries Intersect

Overlap

Boundaries Disjoint

Equal

A

B

Disjoint

Topologicalrelationships

• DISJOINT: boundaries and interiors do not intersect
• 2. TOUCH: boundaries intersect but interiors do not intersect
• 3. OVERLAPBDYDISJOINT: interior of one object intersects boundary and interior of other object, but two boundaries do not intersect (example: a line originates outside a polygon and ends inside the polygon)
• 4. OVERLAPBDYINTERSECT: boundaries and interiors of the two objects intersect
• 5. EQUAL: the two objects have the same boundary and interior

Topological relationships (cont.d)

6. CONTAINS: interior and boundary of one object is completely contained in the interior of other object

7. COVERS: interior of one object is completely contained in interior of other object and their boundaries intersect

8. INSIDE: opposite of CONTAINS; A INSIDE B implies B CONTAINS A

9. COVEREDBY: opposite of COVERS; A COVEREDBY B implies B COVERS A

10. ANYINTERACT: the objects are non-disjoint

• Find all cities in a selected rectangular area

select c.city, c.pop90

from cities c

where sdo_relate (

c.location,

mdsys.sdo_geometry (2003, null, null,

mdsys.sdo_elem_info_array (1,1003,3),

mdsys.sdo_ordinate_array (-109,37,-102,40)),

'mask=ANYINTERACT') = 'TRUE';

• Find all counties in the state of New Hampshire

select c.county, c.state_abrv

from counties c,

states s

where s.state = 'New Hampshire'

and sdo_relate (c.geom, s.geom,

'mask=INSIDE+COVEREDBY querytype=WINDOW') = 'TRUE';

• Find all counties around county Passaic

select c1.county, c1.state_abrv

from counties c1,

counties c2

where c2.state = 'New Jersey'

and c2.county = 'Passaic'

and sdo_relate (c1.geom, c2.geom,

'mask=TOUCH querytype=WINDOW') = 'TRUE';

• Find all interstates that cross county Passaic in NJ
• Find all interstates that cross a county in Arizona

with pop density <10

This requires compatible indexes on the layers !

select i.interstate

from interstates i, counties c

where c.state = 'New Jersey' and c.county = ‘Passaic’

and sdo_relate (i.geom, c.geom,

'mask=ANYINTERACT querytype=WINDOW') = 'TRUE';

select i.interstate

from interstates i, counties c

where c.state = 'Arizona' and c.poppsqmi < 10

and sdo_relate (i.geom, c.geom,

'mask=ANYINTERACT querytype=JOIN') = 'TRUE';

• IDXTAB1
• Index table to associate with first geometry in operator.
• By default, the primary index table is used.
• IDXTAB2
• Index table to associate with the second geometry in operator
• By default, the primary index table is used.
• Only supported if QUERYTYPE=JOIN

boolean := SDO_WITHIN_DISTANCE

( <geometry-1>,

<geometry-2>,

‘DISTANCE=<n>,

QUERYTYPE=<querytype>

[other optional parameters]’

)

• Performs an exact or approximate query
• Euclidean distance only
• Returns TRUE or FALSE

• GEOMETRY-1
• A column of type SDO_GEOMETRY
• GEOMETRY-2
• Variable or column of type SDO_GEOMETRY
• DISTANCE (required)
• The distance (expressed in the units used for the coordinate system)
• QUERYTYPE (optional)

• Find all cities within a distance from an interstate
• Find interstates within a distance from a city

select c.city, c.state_abrv

from cities c, interstates i

where highway = ‘I4’

and sdo_within_distance (

c.location, i.geom,‘distance=0.5') = 'TRUE';

select i.highway

from interstates i, cities c

where city = 'Tampa'

and sdo_within_distance (

i.geom, c.location,'distance=0.5') = 'TRUE';

• Find all cities within a distance from a state

Also returns all cities in Florida !

select c.city,

c.state_abrv

from cities c,

states s

where s.state='Florida'

and sdo_within_distance (

c.location, s.geom, 'distance=1.5') = 'TRUE';

boolean := SDO_NN

( <geometry-1>,

<geometry-2>,

‘SDO_NUM_RES=<n>,

[other optional parameters]’

)

• Calculates the N closest geometries
• Euclidean distance only
• Returns TRUE or FALSE

• GEOMETRY-1
• A column of type SDO_GEOMETRY
• GEOMETRY-2
• Variable or column of type SDO_GEOMETRY
• SDO_NUM_RES (required)
• Number of objects to select

• Find the 5 nearest cities from Orlando

select c1.city, c1.state_abrv

from cities c1, cities c2

where c2.city = 'Orlando'

and sdo_nn (

c1.location, c2.location,

'sdo_num_res = 6') = 'TRUE'

and c1.rowid <> c2.rowid;

• Find the 10 nearest cities from Orlando ordered by distance

select c1.city, c1.state_abrv,

sdo_geom.sdo_distance (

c1.location, c2.location, 0.005) distance

from cities c1, cities c2

where c2.city = 'Orlando'

and sdo_nn (

c1.location, c2.location,

'sdo_num_res = 11') = 'TRUE'

and c1.rowid <> c2.rowid

order by distance;