You can use SDO_GEOM.SDO_CENTROID
(documentation) to find the centroid of a geometry.
Note that the centroid provided by this function is the mathematical centroid only and may not always lie inside the geometry, for example, if your polygon is L shaped. SpatialDB Adviser has a good article on this, but here's a quick illustration:
If this isn't a problem for you and you don't need that level of accuracy, just use the built-in, but if you do consider this to be a problem (as I did in the past), then SpatialDB Adviser has a standalone PL/SQL package that corrrectly calculates centroids.
Depending on your performance needs, you could calculate the centroids on-the-fly and just use them in your query directly, or alternatively, add a centroid column to the table and compute and cache the values with application code (best case) or trigger (worst case).
Your query would look something like this:
SELECT a.*
FROM city.zoning a
JOIN username.buildings b ON sdo_contains(a.geom, b.centroid) = 'TRUE'
WHERE b.bldg_code = 3
Note that this is using SDO_CONTAINS
on the basis of the a.geom
column being spatially indexed and a new column b.centroid
that has been added and populated (note - query not tested). If the zoning geometry is not spatially indexed, then you would need to use SDO_GEOM.RELATE
, or index the centroid column and invert the logic to use SDO_INSIDE
.