// in this example we have a parent model "Collection",
// a child model "CollectionItem"
// and we want to query for a list of up to 100 of the first 
// items for a given collection:
res, err := store.Query(query.Query{
  Limit:  100,
  Offset: 0,
  // CollectionItem keys take the form /Collection:[id]/CollectionItem:[id]
  // and Collections have the key /Collection:[id]
  // the Collection key is the prefix for looking up keys
  Prefix: collection.Key().String(),
  Filters: []query.Filter{
    // Pass in a Filter Type to specify that results must be of type CollectionItem
    // In abstract terms this combined with the Prefix query param amounts to querying:
    // /Collection:[id]/CollectionItem:*
    sql_datastore.FilterKeyTypeEq(CollectionItem{}.DatastoreType()),
  },
  Orders: []query.Order{
    query.OrderByValue{
      // order the collection by the "index" param.
      // this will translate in SQL to "ORDER BY index", so long as
      // the query the CollectionItem model passes back accepts it.
      // see sql_datastore.go for more info. 
      TypedOrder: sql_datastore.OrderBy("index"),
    },
  },
})