docs-devsite/database.query.md
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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 DataSnapshot<!-- -->s 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.
<b>Signature:</b>
export declare interface Query
| Property | Type | Description |
|---|---|---|
| ref | DatabaseReference | The <code>DatabaseReference</code> for the <code>Query</code>'s location. |
| 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 <code>FirebaseApp</code>.<!-- -->Two <code>DatabaseReference</code> objects are equivalent if they represent the same location and are from the same instance of <code>FirebaseApp</code>.<!-- -->Two <code>Query</code> objects are equivalent if they represent the same location, have the same query parameters, and are from the same instance of <code>FirebaseApp</code>. 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 <code>toString()</code> method returns a URL that is ready to be put into a browser, curl command, or a <code>refFromURL()</code> call. Since all of those expect the URL to be url-encoded, <code>toString()</code> 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. |
The DatabaseReference for the Query<!-- -->'s location.
<b>Signature:</b>
readonly ref: DatabaseReference;
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.
<b>Signature:</b>
isEqual(other: Query | null): boolean;
| Parameter | Type | Description |
|---|---|---|
| other | Query | null | The query to compare against. |
<b>Returns:</b>
boolean
Whether or not the current and provided queries are equivalent.
Returns a JSON-serializable representation of this object.
<b>Signature:</b>
toJSON(): string;
<b>Returns:</b>
string
A JSON-serializable representation of this object.
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.
<b>Signature:</b>
toString(): string;
<b>Returns:</b>
string
The absolute URL for this location.