React Query Database Query: Frequently Asked Questions

React Query Database Query: FAQ, specific code examples required

Introduction:
React Query is a powerful tool for handling data query and management . It provides functionality to simplify asynchronous data retrieval, caching and updating. When we use React Query to perform database queries, there are some common problems that arise. This article will answer these questions and provide specific code examples.

1. How to perform basic database queries?

React Query provides the useQuery hook function for initiating basic database queries. We can execute this function by defining a query function and then calling useQuery in the component. The following is an example:

import { useQuery } from 'react-query';
import axios from 'axios';

const fetchUsers = async () => {
  const response = await axios.get('/api/users');
  return response.data;
}

function UsersList() {
  const { data, isLoading, isError } = useQuery('users', fetchUsers);

  if (isLoading) {
    return <div>Loading...</div>;
  }

  if (isError) {
    return <div>Error!</div>;
  }

  return (
    <ul>
      {data.map(user =>
        <li key={user.id}>{user.name}</li>
      )}
    </ul>
  );
}

In the above code, we define a fetchUsers function, which initiates a GET request through axios to obtain user data. We then use useQuery in the UsersList component to execute the function and use the returned data to render the user list in the page.

2. How to handle database queries with parameters?

Sometimes, we need to pass some parameters in the query to filter based on different conditions. React Query provides a convenient way to handle database queries with parameters. Here is an example:

import { useQuery } from 'react-query';
import axios from 'axios';

const fetchUsersByRole = async (role) => {
  const response = await axios.get(`/api/users?role=${role}`);
  return response.data;
}

function UsersList({ role }) {
  const { data, isLoading, isError } = useQuery(['users', role], () => fetchUsersByRole(role));

  // ...
}

In the above code, we changed the fetchUsers function so that it accepts a role parameter and passes it to the API as a query string. In the UsersList component, we use ['users', role] as the first parameter of useQuery to identify the unique identifier for the query. In this way, when the role changes, React Query will automatically re-initiate the query.

3. How to perform parallel database queries?

In some cases, we need to initiate multiple database queries at the same time, and then process the results uniformly after all queries are completed. React Query provides useQueries hook function to handle parallel database queries. The following is an example:

import { useQueries } from 'react-query';
import axios from 'axios';

const fetchUser = async (id) => {
  const response = await axios.get(`/api/users/${id}`);
  return response.data;
}

function UsersList({ ids }) {
  const queries = useQueries(
    ids.map(id => ({
      queryKey: ['user', id],
      queryFn: () => fetchUser(id),
    }))
  );

  // ...
}

In the above code, we define a fetchUser function to query user information based on user id. In the UsersList component, we use useQueries to initiate multiple database queries at the same time and store the query results in queries. Each query is configured through an object, where queryKey is used to uniquely identify the query and queryFn is used to specify the query function.

Conclusion:
React Query is a powerful tool for simplifying database queries and data management. By using useQuery, useQueries and some simple configuration, we can easily build complex database queries. I hope this article helps you when using React Query for database queries. If you have any questions, please feel free to leave a message.

The above is the detailed content of React Query Database Query: Frequently Asked Questions. For more information, please follow other related articles on the PHP Chinese website!