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Two Steps Retrieval

Important

Two Step Retrieval loads only a partial set of the related objects (default size of the retrieved related collection is 10). To load additional related objects, use the Relation Paging API.

With this approach a collection of related objects for a specific relation property in a parent object is retrieved from the server. The client application must know parent object's objectId. The API loads a collection of related children for one property at a time. Child objects retrieved in paged sets, see the Relation Paging API sectionfor additional details.

GET https://api.backendless.com/[application-id]/[REST-api-key]/data/[TABLE-NAME]/[OBJECT-ID]/[relatedPropertyName]?  
   sortBy=[sortingPropertiesList]&props=[retrievalPropertiesList]

where:

Argument                Description
[application-id] the ID of your application generated upon its creation. You can obtain the value in the Manage > App Settings section of the Backendless Console.
[REST-api-key] REST API key of your application. You can obtain the value in the Manage > App Settings section of the Backendless Console.
[TABLE-NAME] name of the table where the data is to loaded from.
[OBJECT-ID] ID of the object for which to load specified relations.
[relatedPropertyName] name of a related property to load. For example, if table Person has a relation column homeAddress pointing to an object in the Address table, the value would be homeAddress.
[sortingPropertiesList] Optional argument. If provided, must contain one or more properties separated by comma. The specified properties will be used by the server to sort the resulting collection by. To request the descending sort order for a property, add the DESC keyword after the property name separated with space, for example sortBy=name DESC. When specifying multiple properties. the comma between the  property names must be URL-encoded as %2C.
[retrievalPropertiesList] Optional argument. If provided, must contain one or more properties from the related table which should be returned in every object included into the response. When specifying multiple properties. the comma between the  property names must be URL-encoded as %2C.

In addition to the GET request documented above, the same API is available with a POST operation where the sortingPropertiesList and the retrievalPropertiesListare in the request body as opposed to the request URL:

Method:

POST

URL:

https://api.backendless.com/[application-id]/[REST-api-key]/data/[TABLE-NAME]/[OBJECT-ID]/[relatedPropertyName]

Request Headers:

user-token: value-of-the-user-token-header-from-login  
Content-Type:application/json

where:

Argument                Description
user-token Optional header. Contains a value returned by Backendless in a preceding user Login API call. If user-token is set in the request, the operation will be executed with the security policy associated with the currently logged in user. This means all permissions associated with the user and the roles assigned to the user will be enforced by Backendless.
Content-Type Must be set to application/json. This header is mandatory.

Request Body:

{  
 "sortBy":"sortingPropertiesList",   
 "props":"retrievalPropertiesList"  
}

where:

Argument                Description
sortingPropertiesList Must contain one or more properties separated by comma. The specified properties will be used by the server to sort the resulting collection by. To request the descending sort order for a property, add the DESC keyword after the property name separated with space, for example sortBy=name DESC.
retrievalPropertiesList Must contain one or more properties from the related table which should be returned in every object included into the response.

Suppose the Person table has a one-to-many relationship column friends pointing to the Users table. The code below retrieves related BackendlessUser objects for a specific Person object: