Eav model sql select only products with all 3 values?
To select more than one attribute:

FROM attribute AS color
JOIN attribute AS material
  ON color.content_id = material.content_id
   AND color.attribute_id = 'color' AND color.value = 'red'
   AND material.attribute_id = 'material' AND material.value = 'steel'


So much flexibility you can strangle yourself on the long sql queries it generates :-)

For other solutions see eav