GraphQL query to cross reference data - graphql

Question

Please find a basic simplified problem and a question below:
Monopoly Example
Data Types:
USER
name
houses (one-to-many)
STREET
name
HOUSE
street (one-to-one)
Note that in my data model there is no reference between user and streets (maybe monopoly wasn't the best example -.-)
Question:
A user can have several houses on different streets. How can I query a list of streets that a specific user has houses on?
Wanted Result:
{
"data": {
"User": {
"name": "The Hat",
"streets": [
{
name: "Bow Street"
},
{
name: "Oxford Street"
},
{
name: "Park Lane"
},
]
}
}
}
Is that possible?

Answer 1

Fetching relational data like that is typically handled by having nested fields in your query. The ability to traverse the data graph in a query is one of GraphQL's biggest benefits.
In general, this article about GraphQL APIs is a helpful resource to understand how it works.
Let's look at some different possible queries.
Query a list of streets that a specific user has houses on
query {
allStreets(filter: {
house: {
user: {
id: "user-id"
}
}
}) {
name
}
}
Here we make use of a relational filter passed in as an argument to query the streets that are related to a hours that is related to a specific user, which results in:
{
"data": {
"allStreets": [
{
"name": "Bow Street"
},
{
"name": "Oxford Street"
},
{
"name": "Park Lane"
}
]
}
}
We can see that we get back a list of streets. We could also include the house field in the allStreets query to obtain that information as well.
Query a specific user object and a list of streets that it has houses on
query {
User(id: "user-id") {
name
houses {
street {
name
}
}
}
}
Here we specify a user by id, so the top-level object of the result is a single user object. Additionally, we are getting back a list of streets that user has houses on:
{
"data": {
"User": {
"name": "The Hat",
"houses": [
{
"street": {
"name": "Bow Street"
}
},
{
"street": {
"name": "Oxford Street"
}
},
{
"street": {
"name": "Park Lane"
}
}
]
}
}
}
What's notable is that the structure of the response follows the structure of the query precisely.