I've started digging deep into PostgreSQL and PostGIS for a very geo centric project I'm working on.

PostGIS is an extension that provides geo spatial functionality to PostgreSQL.

Let's say you have a table of neighborhoods, where each record contains an id and a list of coordinates that make up the boundary of each neighborhood.

The following query would return the id of the neighborhood the coordinates -117.289 33.949 exists within.

SELECT id FROM neighborhoods
WHERE ST_Contains(neighborhoods.geometry, 
	ST_Transform(
		ST_GeomFromText('POINT(-117.289 33.949)', 4326), 4326
	)
)

That's pretty verbose, so let's make a database function for it.

create or replace function in_neighborhood(coords varchar(255))
returns varchar(255)
as $$
declare
  myid varchar(255);
begin
  SELECT id FROM zones
  WHERE ST_Contains(zones.geometry, ST_Transform(
    ST_GeomFromText(concat('POINT(', coords, ')'), 4326), 4326)
  ) 
  into myid;
  return myid;
end;
$$
language plpgsql;

Now we can achieve the same result as our original query by running the following SQL:

select in_neighborhood('-117.289 33.949');