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querying-from-an-application.md

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Querying from an Application

Once a subgraph is deployed to the Subgraph Studio or to The Graph Explorer, you will be given the endpoint for your GraphQL API that should look something like this:

Subgraph Studio (testing endpoint)

Queries (HTTP)https://api.studio.thegraph.com/query/<ID>/<SUBGRAPH_NAME>/<VERSION>

Graph Explorer

Queries (HTTP)https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>

Using the GraphQL endpoint, you can use various GraphQL Client libraries to query the subgraph and populate your app with the data indexed by the subgraph.

Here are a couple of the more popular GraphQL clients in the ecosystem and how to use them:

Apollo client

Apollo client supports web projects, including frameworks like React and Vue, as well as mobile clients like iOS, Android, and React Native.

Let's look at how to fetch data from a subgraph with Apollo client in a web project.

First, install @apollo/client and graphql:

npm install @apollo/client graphql

Then you can query the API with the following code:

import { ApolloClient, InMemoryCache, gql } from '@apollo/client'
const APIURL = 'https://api.studio.thegraph.com/query//<SUBGRAPH_NAME>/'
const tokensQuery = `  query {    tokens {      id      tokenID      contentURI      metadataURI    }  }`
const client = new ApolloClient({  uri: APIURL,  cache: new InMemoryCache(),})
client  .query({    query: gql(tokensQuery),  })  .then((data) => console.log('Subgraph data: ', data))  .catch((err) => {    console.log('Error fetching data: ', err)  })

To use variables, you can pass in a variables argument to the query:

const tokensQuery = `  query($first: Int, $orderBy: BigInt, $orderDirection: String) {    tokens(      first: $first, orderBy: $orderBy, orderDirection: $orderDirection    ) {      id      tokenID      contentURI      metadataURI    }  }`
client  .query({    query: gql(tokensQuery),    variables: {      first: 10,      orderBy: 'createdAtTimestamp',      orderDirection: 'desc',    },  })  .then((data) => console.log('Subgraph data: ', data))  .catch((err) => {    console.log('Error fetching data: ', err)  })

URQL

Another option is URQL, a somewhat lighter-weight GraphQL client library.

Let's look at how to fetch data from a subgraph with URQL in a web project.

First, install urql and graphql:

npm install urql graphql

Then you can query the API with the following code:

import { createClient } from 'urql'
const APIURL = 'https://api.thegraph.com/subgraphs/name/username/subgraphname'
const tokensQuery = `  query {    tokens {      id      tokenID      contentURI      metadataURI    }  }`
const client = createClient({  url: APIURL,})
const data = await client.query(tokensQuery).toPromise()