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Dependent Queries

useQuery dependent Query

Dependent (or serial) queries depend on previous ones to finish before they can execute. To achieve this, it's as easy as using the enabled option to tell a query when it is ready to run:

'Example'

tsx
// Get the user
const { data: user } = useQuery({
  queryKey: ['user', email],
  queryFn: getUserByEmail,
})

const userId = user?.id

// Then get the user's projects
const {
  status,
  fetchStatus,
  data: projects,
} = useQuery({
  queryKey: ['projects', userId],
  queryFn: getProjectsByUser,
  // The query will not execute until the userId exists
  enabled: !!userId,
})
// Get the user
const { data: user } = useQuery({
  queryKey: ['user', email],
  queryFn: getUserByEmail,
})

const userId = user?.id

// Then get the user's projects
const {
  status,
  fetchStatus,
  data: projects,
} = useQuery({
  queryKey: ['projects', userId],
  queryFn: getProjectsByUser,
  // The query will not execute until the userId exists
  enabled: !!userId,
})

'Example'

The projects query will start in:

tsx
status: 'loading'
fetchStatus: 'idle'
status: 'loading'
fetchStatus: 'idle'

As soon as the user is available, the projects query will be enabled and will then transition to:

tsx
status: 'loading'
fetchStatus: 'fetching'
status: 'loading'
fetchStatus: 'fetching'

Once we have the projects, it will go to:

tsx
status: 'success'
fetchStatus: 'idle'
status: 'success'
fetchStatus: 'idle'

useQueries dependent Query

Dynamic parallel query - useQueries can depend on a previous query also, here's how to achieve this:

'Example2'

tsx
// Get the users ids
const { data: userIds } = useQuery({
  queryKey: ['users'],
  queryFn: getUsersData,
  select: users => users.map(user => user.id),
})

// Then get the users messages
const usersMessages = useQueries({
  queries: userIds
    ? usersId.map(id => {
        return {
          queryKey: ['messages', id],
          queryFn: () => getMessagesByUsers(id),
        };
      })
  : [], // if users is undefined, an empty array will be returned
})
// Get the users ids
const { data: userIds } = useQuery({
  queryKey: ['users'],
  queryFn: getUsersData,
  select: users => users.map(user => user.id),
})

// Then get the users messages
const usersMessages = useQueries({
  queries: userIds
    ? usersId.map(id => {
        return {
          queryKey: ['messages', id],
          queryFn: () => getMessagesByUsers(id),
        };
      })
  : [], // if users is undefined, an empty array will be returned
})

'Example2'

Note that useQueries return an array of query results

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