Spatial SQL with PostGIS and Postgres: What makes spatial queries special?
When you are working with spatial data using the PostGIS extension to Postgres, most of the Standard Query Language (SQL) you end up with is just standard SQL—table joins, selects, inserts, updates, and so on—not spatial sorcery. But there is a small percentage of SQL in PostGIS that makes spatial queries a little bit special! I have collected a few examples to this blog post.
