Inverted Relation Retrieval¶

Backendless supports a special query syntax for loading a subset of child objects for a specific parent. Consider the following table schemas:

PhoneBook table:

phonebook-table-schema

Contact table:

contact-table-schema

Address table:

address-table-schema

These tables will be used to demonstrate how to query Backendless for conditional related object retrieval.

The general structure of a whereClause query to load a collection of child objects for a specific parent object is:

ParentTableName[ relatedColumnName ].parentColumnName COLUMN-VALUE-CONDITION

Both columns relatedColumnName and parentColumnName must be declared in a table with name of ParentTableName. The relatedColumnName must be a relation column. The table relatedColumnName points to is the table where the objects must be loaded from. The examples below demonstrate the usage of this syntax:

Find all contacts in a city for a specific phone book¶

Suppose objectId of the PhoneBook object for which we need to find contacts isXXXX-XXXX-XXXX-XXXX, then the where clause in the query must look as shown below:

PhoneBook[contacts].objectId= 'XXXX-XXXX-XXXX-XXXX' and address.city = 'New York'

The where clause must be URL encoded when submitted in a REST request:

PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20address.city%20%3D%20%27New%20York%27

The final curl command to run the query is:

curl https://xxxx.backendless.app/api/data/Contact?where=PhoneBook%5Bcontacts%5D.objectId%3D%27DC5B7BDD-2AF6-8949-FFB3-56C2093CBC00%27%20and%20address.city%20%3D%20%27New%20York%27

Codeless Reference¶

The following example is identical to the one presented above and uses the following condition in thewhere clause property: This operation is set to retrieve related objects whose city is 'New York'.

PhoneBook[contacts].objectId = 'DB7A04FD-C305-4615-8480-BF75F244F10F' and address.city = 'New York'

data_inverted_relation_retrieval

Important

For a detailed description of all input parameters see the Basic Object Retrieval topic of this guide.

After the Codeless logic runs, the operation returns two objects whose city is 'New York'.

data_inverted_relation_retrieval_2

Find all contacts for the specific phone book where the city name contains letter 'a'¶

Suppose objectId of the PhoneBook object for which we need to find contacts isXXXX-XXXX-XXXX-XXXX, then the where clause in the query must look as shown below:

PhoneBook[contacts].objectId= 'XXXX-XXXX-XXXX-XXXX' and address.city like '%a%'

The where clause must be URL encoded when submitted in a REST request:

PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20address.city%20like%20%27%25a%25%27

The final curl command to run the query is:

curl https://xxxx.backendless.app/api/data/Contact?where=PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20address.city%20like%20%27%25a%25%27

Codeless Reference¶

The following example is identical to the one presented above and uses the following condition in thewhere clause property. This operation is set to retrieve related objects whose name of the city contains at least one letter 'a'.

PhoneBook[contacts].objectId = 'DB7A04FD-C305-4615-8480-BF75F244F10F' and address.city like '%a%'

data_inverted_relation_retrieval

After the Codeless logic runs, the operation returns four objects that have at least one letter 'a' in the name of the city.

data_inverted_relation_retrieval_3

Find all contacts where age is greater than 20 for a specific phone book¶

Suppose objectId of the PhoneBook object for which we need to find contacts isXXXX-XXXX-XXXX-XXXX, then the where clause in the query must look as shown below:

PhoneBook[contacts].objectId= 'XXXX-XXXX-XXXX-XXXX' and age > 20

The where clause must be URL encoded when submitted in a REST request:

PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%2020

The final curl command to run the query is:

curl https://xxxx.backendless.app/api/data/Contact?where=PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%2020

Codeless Reference¶

The following example is identical to the one presented above and uses the following condition in thewhere clause property: This operation is set to retrieve related objects whose age is greater than 20.

PhoneBook[contacts].objectId = 'DB7A04FD-C305-4615-8480-BF75F244F10F' and age > 20

data_inverted_relation_retrieval

After the Codeless logic runs, the operation returns four objects that match the where clause condition. As you can see, the value in the age property is greater than 20.

data_inverted_relation_retrieval_4

Find all contacts for a specific phone book where age is within the specified range¶

Suppose objectId of the PhoneBook object for which we need to find contacts isXXXX-XXXX-XXXX-XXXX, then the where clause in the query must look as shown below:

PhoneBook[contacts].objectId= 'XXXX-XXXX-XXXX-XXXX' and age >= 21 and age <= 30

The where clause must be URL encoded when submitted in a REST request:

PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%3D%2021%20and%20age%20%3C%3D%2030

The final curl command to run the query is:

curl https://xxxx.backendless.app/api/data/Contact?where=PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%3D%2021%20and%20age%20%3C%3D%2030

Codeless Reference¶

The following example is identical to the one presented above and uses the following condition in thewhere clause property: This operation is set to retrieve related objects using the age properties whose values are in range between 21 and 30 .

PhoneBook[contacts].objectId = 'DB7A04FD-C305-4615-8480-BF75F244F10F' and age >= 21 and age <= 30

data_inverted_relation_retrieval

After the Codeless logic runs, the operation returns only one object since it matches the where clause condition.

data_inverted_relation_retrieval_5

Find all contacts for a specific phone book where age is greater than 20 and the city is Tokyo¶

Suppose objectId of the PhoneBook object for which we need to find contacts isXXXX-XXXX-XXXX-XXXX, then the where clause in the query must look as shown below:

PhoneBook[contacts].objectId= 'XXXX-XXXX-XXXX-XXXX' and age > 21 and address.city = 'Tokyo'

The where clause must be URL encoded when submitted in a REST request:

PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%2021%20and%20address.city%20%3D%20%27Tokyo%27

The final curl command to run the query is:

curl https://xxxx.backendless.app/api/data/Contact?where=PhoneBook%5Bcontacts%5D.objectId%3D%20%27XXXX-XXXX-XXXX-XXXX%27%20and%20age%20%3E%2021%20and%20address.city%20%3D%20%27Tokyo%27

Codeless Reference¶

The following example is identical to the one presented above and uses the following condition in thewhere clause property: This operation is set to retrieve related objects using the age properties whose values is greater than 21, and also the city properties whose value is 'Tokyo'.

PhoneBook[contacts].objectId = 'DB7A04FD-C305-4615-8480-BF75F244F10F' and age > 21 and address.city = 'Tokyo'

data_inverted_relation_retrieval

After the Codeless logic runs, the operation returns only one object matching the where clause condition.

data_inverted_relation_retrieval_6