A 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 DatabaseReference, you can receive data from a Query by using the on*() methods. You will only receive events and DataSnapshots for the subset of the data that matches your query.
See https://firebase.google.com/docs/database/web/lists-of-data#sorting_and_filtering_data for more information.
Signature:
export declare interface Query
Properties
| Property | Type | Description |
|---|---|---|
| ref | DatabaseReference | The DatabaseReference for the Query's location. |
Methods
| Method | Description |
|---|---|
| isEqual(other) | Returns whether or not the current and provided queries represent the same location, have the same query parameters, and are from the same instance of FirebaseApp.Two DatabaseReference objects are equivalent if they represent the same location and are from the same instance of FirebaseApp.Two Query objects are equivalent if they represent the same location, have the same query parameters, and are from the same instance of FirebaseApp. Equivalent queries share the same sort order, limits, and starting and ending points. |
| toJSON() | Returns a JSON-serializable representation of this object. |
| toString() | Gets the absolute URL for this location.The toString() method returns a URL that is ready to be put into a browser, curl command, or a refFromURL() call. Since all of those expect the URL to be url-encoded, toString() returns an encoded URL.Append '.json' to the returned URL when typed into a browser to download JSON-formatted data. If the location is secured (that is, not publicly readable), you will get a permission-denied error. |
Query.ref
The DatabaseReference for the Query's location.
Signature:
readonly ref: DatabaseReference;
Query.isEqual()
Returns whether or not the current and provided queries represent the same location, have the same query parameters, and are from the same instance of FirebaseApp.
Two DatabaseReference objects are equivalent if they represent the same location and are from the same instance of FirebaseApp.
Two Query objects are equivalent if they represent the same location, have the same query parameters, and are from the same instance of FirebaseApp. Equivalent queries share the same sort order, limits, and starting and ending points.
Signature:
isEqual(other: Query | null): boolean;
Parameters
| Parameter | Type | Description |
|---|---|---|
| other | Query | null | The query to compare against. |
Returns:
boolean
Whether or not the current and provided queries are equivalent.
Query.toJSON()
Returns a JSON-serializable representation of this object.
Signature:
toJSON(): string;
Returns:
string
A JSON-serializable representation of this object.
Query.toString()
Gets the absolute URL for this location.
The toString() method returns a URL that is ready to be put into a browser, curl command, or a refFromURL() call. Since all of those expect the URL to be url-encoded, toString() returns an encoded URL.
Append '.json' to the returned URL when typed into a browser to download JSON-formatted data. If the location is secured (that is, not publicly readable), you will get a permission-denied error.
Signature:
toString(): string;
Returns:
string
The absolute URL for this location.