Query sorts and filters the data at a Database location so only a subset
of the child data is included. This can be used to order a collection of
data by some attribute (for example, height of dinosaurs) as well as to
restrict a large list of items (for example, chat messages) down to a number
suitable for synchronizing to the client. Queries are created by chaining
together one or more of the filter methods defined here.
Just as with a
Reference, you can receive data from a
Query by using the
on() method. You will only receive events and
DataSnapshots for the
subset of the data that matches your query.
See Sorting and filtering data for more information.