Differentiating polygons in OSM data
A reminder of the syntax used in SQL query language helps to clear our minds as we generate complex questions within and between datasets:
SELECT name_attribute: What is the attribute you are selecting from your dataset?FROM name_table: What table are you selecting this attribute from?WHERE: What conditions need to be met?GROUP BY name_attribute: Should they be sorted by name, area, or ID for example?HAVING: Additional criteria to be met, often a threshold value.
Try to recognize this template in queries you observe or create. There should be a story embedded in each query.
Spatial queries
How does PostGIS extract information from a database? Recall that we are querying coordinates, reference systems, and other dimensions from a wide variety of datasets of different geometries that include the length of a line, the area of a polygon, or even a point location. These are collected based on specific properties...
