gistfile1.txt

#wifi {
     [type='Free']  {marker-fill:black}
     [type!='Free'] {marker-fill:red}
     marker-width:5;
     marker-line-color:white;
}


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SELECT * FROM wifi WHERE type='Free' AND zip='10010'

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SELECT * FROM wifi ORDER BY the_geom <-> ST_GeomFromText('POINT(-73.989418 40.7393)',4326) limit 100


http://viz2.cartodb.com/api/v1/sql?q=

SELECT cartodb_id,ST_distance(ST_GeomFromText('POINT(-73.989418 40.7393)',4326)::geography,the_geom::geography) as distance_to_office,st_x(the_geom) as lon,st_y(the_geom) as lat  FROM wifi ORDER BY distance_to_office ASC LIMIT 10


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SELECT * FROM parks as p WHERE (SELECT count(*) FROM wifi as w WHERE ST_Intersects(w.the_geom,p.the_geom))>0

--------------------------------------------------


#parks{
      	polygon-fill:#FFF;
              line-width:1;
              polygon-opacity:1;
              line-opacity:0.2;
              polygon-pattern-file:url(/home/ubuntu/tile_assets/patt1.png);

                text-name:"[signname]";
                text-face-name:"DejaVu Sans Book";
                text-size:12;
                text-halo-radius:1;
                text-fill:#333;
                text-halo-fill:rgba(255,255,255,1);
   	     text-wrap-width: 100;
                text-allow-overlap:false;
         	     text-placement-type:simple;
   	    text-avoid-edges:true;
        	
}

BONUS:

UPDATE nyct2000 as f  SET num_stop_frisk=(SELECT count(*) from stop_frisk as w WHERE ST_Intersects(f.the_geom,w.the_geom))/ST_Area(the_geom)