var metals = new Firebase("https://<dbname>.firebaseio.com/metals").limit(3);这提供了列表中的最后3项。所以为了获得第一个3条目,我认为这会有效,但它会破坏.
var metals = new Firebase("https://<dbname>.fireb
.*, metals.*
`locations`
gems ON locations.locatable_id = gems.id AND locations.locatable_type= 'Gem'
metals ON locations.locatable_id = metals.id AND locations.locatable_type = 'Metallocations.longitude BETWEEN -1.0000 AND -2.0