76 lines
2.7 KiB
Markdown
76 lines
2.7 KiB
Markdown
- Insert all Census Tracts from Lower Manhattan and nearby areas within the supplied bounding box to a table named `manhattan_census_tracts` which has columns `the_geom` (geometry) and `geom_refs` (text).
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```sql
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INSERT INTO manhattan_census_tracts(the_geom, geom_refs)
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SELECT *
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FROM OBS_GetBoundariesByGeometry(
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ST_MakeEnvelope(-74.0251922607,40.6945658517,
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-73.9651107788,40.7377626342,
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4326),
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'us.census.tiger.census_tract')
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```
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- Insert points that lie on Census Tracts from Lower Manhattan and nearby areas within the supplied bounding box to a table named `manhattan_tract_points` which has columns `the_geom` (geometry) and `geom_refs` (text).
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```sql
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INSERT INTO manhattan_tract_points (the_geom, geom_refs)
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SELECT *
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FROM OBS_GetPointsByGeometry(
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ST_MakeEnvelope(-74.0251922607,40.6945658517,
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-73.9651107788,40.7377626342,
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4326),
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'us.census.tiger.census_tract')
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```
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- Overwrite a point geometry with a boundary geometry that contains it in your table
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```SQL
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UPDATE tablename
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SET the_geom = OBS_GetBoundary(the_geom, 'us.census.tiger.block_group')
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```
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- Write the US Census block group geoid that contains the point geometry for every row as a new column in your table.
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```SQL
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UPDATE tablename
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SET geometry_id = OBS_GetBoundaryId(the_geom, 'us.census.tiger.block_group')
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```
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- Use a table of `geometry_id`s (e.g., geoid from the U.S. Census) to select the unique boundaries that they correspond to and insert into a table called, `overlapping_polygons`. This is a useful method for creating new choropleths of aggregate data.
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```SQL
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INSERT INTO overlapping_polygons (the_geom, geometry_id, point_count)
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SELECT
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OBS_GetBoundaryById(geometry_id, 'us.census.tiger.county') As the_geom,
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geometry_id,
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count(*)
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FROM tablename
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GROUP BY geometry_id
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```
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- Insert into table `denver_census_tracts` the census tract boundaries and geom_refs of census tracts which intersect within 10 miles of downtown Denver, Colorado.
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```sql
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INSERT INTO denver_census_tracts(the_geom, geom_refs)
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SELECT *
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FROM OBS_GetBoundariesByPointAndRadius(
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CDB_LatLng(39.7392, -104.9903), -- Denver, Colorado
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10000 * 1.609, -- 10 miles (10km * conversion to miles)
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'us.census.tiger.census_tract')
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```
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- Insert into table `denver_tract_points` points on US census tracts and their corresponding geoids for census tracts which intersect within 10 miles of downtown Denver, Colorado, USA.
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```sql
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INSERT INTO denver_tract_points(the_geom, geom_refs)
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SELECT *
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FROM OBS_GetPointsByPointAndRadius(
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CDB_LatLng(39.7392, -104.9903), -- Denver, Colorado
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10000 * 1.609, -- 10 miles (10km * conversion to miles)
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'us.census.tiger.census_tract')
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``` |