Object Relational Model Spatial Queries - PowerPoint PPT Presentation

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Object Relational Model Spatial Queries

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  1. Object Relational ModelSpatial Queries

  2. 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 Query Model Exact Result Set

  3. Spatial Operators vs Functions • 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

  4. SDO_RELATE 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 Spatial Operators vs Functions Operators Functions

  5. Spatial Operators

  6. The SDO_RELATE operator 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

  7. Required arguments • 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

  8. 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

  9. 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

  10. 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

  11. SDO_RELATE - An example • 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';

  12. SDO_RELATE - A window query • 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';

  13. SDO_RELATE - Another window query • 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';

  14. SDO_RELATE - join vs window query • 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';

  15. Optional arguments • 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

  16. The SDO_WITHIN_DISTANCE operator 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

  17. Arguments • 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)

  18. SDO_WITHIN_DISTANCE Examples • 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';

  19. SDO_WITHIN_DISTANCE Examples • 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';

  20. The SDO_NN operator 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

  21. Arguments • 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

  22. SDO_NN Example • 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;

  23. SDO_NN Example • 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;