Count Points in Polygon with Postgis

I've got a simple problem: I want to count the number of points within a set of polygons.

I have a SQL already but it only gives back the gid of the polygone that actually contains points.

My tables: a polygon layer with 19.000 rows and a point layer with 450 rows.

The following SQL

select grid.gid, count(*) AS totale FROM grid, kioskdhd3 WHERE 
st_contains(grid.geom,kioskdhd3.geom) GROUP BY grid.gid;

return only some 320 polygons that actually contain points. But I want all polygons returned, even thought the number of points is 0.

Of course it has to do with my WHERE-clause. Where do I have to put in my st_contains?

Thank you Carsten

Answer

SELECT grid.gid, count(kioskdhd3.geom) AS totale 
FROM grid LEFT JOIN kioskdhd3 
ON st_contains(grid.geom,kioskdhd3.geom) 
GROUP BY grid.gid;