Use Node.js to connect to the database and query

With the popularity of JavaScript and the rise of Node.js, more and more developers are beginning to use Node.js to write server-side applications. These applications often require the use of databases to store various data. So, how to use Node.js to connect to the database and query it? Next, this article will introduce in detail the process of connecting Node.js to database query.

1. Database selection

Before using Node.js to connect to the database, we first need to choose a database. Node.js supports many database types, including MongoDB, MySQL, Oracle, PostgreSQL, etc. We need to choose a database that suits us according to our needs. For example, if we need to store a large amount of unstructured data, then MongoDB is more suitable; if we need to perform transaction processing, then MySQL or PostgreSQL is more suitable.

2. Install the database driver

No matter which database we choose, we need to use the database driver. In Node.js, there are many third-party database drivers to choose from, such as MySQL's mysql module and MongoDB's mongodb module. We need to install the corresponding database driver in the Node.js project.

Taking MySQL as an example, the steps to use the MySQL driver in Node.js are as follows:

1. Install the mysql module

Use the npm command to install ：

npm install mysql

2. Load the mysql module

Load the mysql module in Node.js code:

var mysql = require('mysql');

3. Create a connection

Use the mysql module to create a database connection:

var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : 'password',
  database : 'database_name'
});

Among them, host, user, password, and database represent the address, user name, password, and database name of the database respectively.

4. Query

Use the connection object to query:

connection.query('SELECT * FROM table_name', function (error, results, fields) {
  if (error) throw error;
  console.log('The result is: ', results);
});

The first parameter is the query statement, and the second parameter is the callback function , used to process query results.

3. Example

The following is a complete example that demonstrates how to use Node.js to connect to the MySQL database and query:

var mysql = require('mysql');

var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : 'password',
  database : 'database_name'
});

connection.connect();

connection.query('SELECT * FROM table_name', function (error, results, fields) {
  if (error) throw error;
  console.log('The result is: ', results);
});

connection.end();

First, we loaded the mysql module , and then create a database connection using the createConnection function. Next, we use the connect function to connect to the database, then use the query function to query, and process the query results in the callback function. Finally, we close the database connection using the end function.

4. Summary

This article introduces how to use Node.js to connect to the database and perform queries. The steps to connect to a database using Node.js are roughly the same. You just need to install the corresponding driver according to the database type you choose.

The above is the detailed content of Use Node.js to connect to the database and query. For more information, please follow other related articles on the PHP Chinese website!