Not getting the desired amount of rows. Help!

Hi all!
I have a database wich has a table named 'productos', filled with 31 of them. I run a query (with JOINS) and it only returns me 20 rows. I want the 31 productos even if the SUM´s are zero or nonexistent. I guess I am doing something wrong with the joins or have a theory problem. Any help is appreciated.

The query:

SELECT productos.producto_id, SUM( ingreso_mes_1 + ingreso_mes_2 + ingreso_mes_3 + ingreso_mes_4 + ingreso_mes_5 + ingreso_mes_6 + ingreso_mes_7 + ingreso_mes_8 + ingreso_mes_9 + ingreso_mes_10 + ingreso_mes_11 + ingreso_mes_12) AS ingreso, SUM(costo_mes_1 + costo_mes_2 + costo_mes_3 + costo_mes_4 + costo_mes_5 + costo_mes_6 + costo_mes_7 + costo_mes_8 + costo_mes_9 + costo_mes_10 + costo_mes_11 + costo_mes_12) AS costo
FROM productos
LEFT JOIN ventas
USING ( producto_id)
LEFT JOIN clientes
USING (cliente_id)
WHERE clientes.canal_id = 1
AND ventas.destino_id = 1
GROUP BY productos.producto_id

Thanks!

*If you need additional info, just ask.

I am a little vague on what you are trying to do, but I think that you do have a problem with your joins. You may need to segregate them, something like this:

SELECT productos.producto_id, SUM( ingreso_mes_1 + ingreso_mes_2 + ingreso_mes_3 + ingreso_mes_4 + ingreso_mes_5 + ingreso_mes_6 + ingreso_mes_7 + ingreso_mes_8 + ingreso_mes_9 + ingreso_mes_10 + ingreso_mes_11 + ingreso_mes_12) AS ingreso, SUM(costo_mes_1 + costo_mes_2 + costo_mes_3 + costo_mes_4 + costo_mes_5 + costo_mes_6 + costo_mes_7 + costo_mes_8 + costo_mes_9 + costo_mes_10 + costo_mes_11 + costo_mes_12) AS costo
FROM (productos LEFT JOIN ventas USING (producto_id))
LEFT JOIN clientes
USING (cliente_id)
WHERE clientes.canal_id = 1
AND ventas.destino_id = 1
GROUP BY productos.producto_id

HTH,
Russ