[doc] improve a bit the README file to give query examples

README

@@ -23,12 +23,17 @@ It introduces one new type when defining attributes in the data model schema:
   * ``coord_dimension``. The number of dimensions used by geometries. Defaults
     to 2.
 
+* a ``Geography`` type (see the description_).
+
+.. _description: https://postgis.net/docs/using_postgis_dbmanagement.html#PostGIS_Geography
+
+
 Then you can also use geometric functions like ``ST_INTERSECTS``, ``ST_WITHIN``
 or ``ST_UNION`` to work with this new type.
 
 See `Postgis manual`_ for reference documentation about Postgis.
 
-.. _Postgis manual: http://postgis.net/docs/manual-2.0/ 
+.. _Postgis manual: http://postgis.net/docs/
 
 
 Example
@@ -41,3 +46,21 @@ In ``schema.py``, one can declare a ``City`` entity like the following.
     class City(EntityType):
         name = String(required=True)
         geometry = Geometry(geom_type='POLYGON', srid=4326)
+
+You may then make queries like:
+
+.. code-block:: python
+
+   # get all cities in a given bounding box
+   rql('City C WHERE C geometry G HAVING(ST_WITHIN(G, ST_MAKEENVELOPE('
+       '%(left)s, %(bottom)s, %(right)s, %(top)s, 4326)) = TRUE)',
+	   {'left': 2.2,
+	   'right': 2.6,
+	   'top': 49,
+	   'bottom': 48})
+
+   # get all cities at a given distance from a point, sorted by distance
+   rql('Any C, ST_DISTANCE(G, ST_SETSRID(ST_MAKEPOINT(2.2, 48.4), 4326)) '
+       'ORDERBY 5 WHERE '
+	   'C geometry G HAVING ('
+	   ' ST_DWITHIN(G, ST_SETSRID(ST_MAKEPOINT(2.2, 48.4), 4326), 0.1) = TRUE)')