Queries
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A GraphQL query is used for fetching data. This can be useful for verifying which data is stored for a given object class, or for a third party to export data from your solution.
The simplest query you can run is to specify the object class (known as an object type in GraphQL). For example, if you wanted to list all Projects in the database, you could write:
Note that the name of the object class is specified under Endpoint Name in the object class properties in Appfarm Create.
Click the Play button (or Cmd/Ctrl + Enter) to execute the query. The response will be displayed to the right.
The query editor will also edit your query to contain all the properties (fields in GraphQL) that are available to query:
You can use these fields in your query to customize the response that you receive. For example, the following query will only return the id and title properties of each project:
To further refine your query you can include arguments, see advanced queries.
If a queried object references another object, or is referenced by another object, you can extract details about the other object.
For example, if you have projects with tasks, you might like to list out the tasks for a project, or obtain the project details for a given task.
More advanced query operators can be used to further customize the response. In the following examples, Book is queried in different ways.
Restrict the response to contain only n
objects.
Skip the first n
objects in the response.
Sort the response in ascending (ASC) or descending (DESC) order.
Combine operators to filter the response.
The supported filter operators are and
, or
, not
, nor
, eq
, ne
, in
, nin
, gt
, gte
, lt
, lte
. Each filter operator will be explained by example:
Example:
This query will return all books where
the pages
field is greater than 500
and the pages
field is less than or equal 1000
Example:
This query will return all books where
the pages
field is greater than 500
and the pages
field is less than or equal 1000
or
the title
field equals Jane Eyre
Example:
This query will return all books where
the pages
field is not greater than 500
(in other words, 499 or less)
Example:
This query will return all books that
contain the price
field whose value is not equal to 1.99
and contain the sale
field whose value is not equal to true
or
contain the price
field whose value is not equal to 1.99
but do not contain the sale
field or
do not contain the price
field but contain the sale
field whose value is not equal to true
or
do not contain the price
field and do not contain the sale
field
This operator is used for comparison. Example:
This query will return all books where
the title
field equals Jane Eyre
This operator is used for comparison. Example:
This query will return all books where
the title
field not equals Jane Eyre
This operator is used for comparison. Example:
This query will return all books where
the title
field is any ofJane Eyre
or Wuthering Heights
(or rephrased: the value of the title
field is in the set of the values Jane Eyre
and Wuthering Heights
)
This operator is used for comparison. Example:
This query will return all books where
the title
field is none ofJane Eyre
or Wuthering Heights
(or rephrased: the value of the title
field is not in the set of the values Jane Eyre
and Wuthering Heights
)
This operator is used for comparison. Example:
This query will return all books where
the pages
field is greater than 500
(i.e. 501 pages or more)
This operator is used for comparison. Example:
This query will return all books where
the pages
field is greater than or equal 500
(i.e. 500 pages or more)
This operator is used for comparison. Example:
This query will return all books where
the pages
field is less than 500
(i.e. 499 pages or less)
This operator is used for comparison. Example:
This query will return all books where
the pages
field is less than or equal 500
(i.e. 500 pages or less)
You can query the total number of objects in a response by using the Count query type. This needs to be enabled per object class by selecting Enable Aggregate and granting the Aggregate permission to the appropriate role.
When enabled, a new query type is added to your available queries. Using the object class Order as an example, we would get access to countOrder. This is separate to the order query type for reading data.
You can summarize or find average, min/max or standard deviation using GraphQL aggregates. You may also group the records. For example, you may find the total order amount from OrderLines per Product:
Given the above example with an OrderLine object class, you may perform the following:
Filter, Sort or Group on any property (optional)
In the list of properties to be returned, you may select the first or last entry. For example, we might return customer_first
or customer_last
for in the above expression for returning the first or last customer of the grouped list of order lines.
In the list of properties to be returned, we may select the following aggregates of numbers (with amount
as example):
amount_sum
(sum of the amount of orderLines)
amount_avg
(average of the amount of orderLines)
amount_max
(maximum of the amount of orderLines)
amount_min
(minimum of the amount of orderLines)
amount_stdDevPop
(standard deviation of the amount of all orderLines / the whole population)
amount_stdDevSamp
(standard deviation of the amount of orderLines in the returned sample)
amount_first
(amount of the first orderLine)
amount_last
(amount of the last orderLine)
You may select to return an alias for a property, as in the above example sum: amount_sum
(sum
is an alias for amount_sum
)
Following the example above, records can also be grouped by multiple properties. For instance, finding the total order amount from OrderLines per product and size. This will return one aggregation per unique pair of values for product and size:
GraphQL aggregations may be handy in applications with large amounts of data. With aggregation in GraphQL you may aggregate data on database level before it is returned to the client.
It is pretty straight forward.
Create an API Key in Appfarm Create. Go to Service Accounts in Appfarm Create, and locate (or create) a Service Account that is member of a Role with Read
and Aggregate
Permissions to the Object Classes to be queried in GraphQL
Use the Web Request to run the Query:
URL: https://<HOSTNAME>/api/graphql
Query Parameters: 1 parameter named query
. Paste the query itself (e.g. {aggregateOrderLine(filter: ...)}
as value
Result mapping: Map the properties returned from the GraphQL aggregation
Example setup, with mapping of the Sum
to existing Product objects
As with , this needs to be enabled per object class by selecting Enable Aggregate and granting the Aggregate permission to the appropriate role.