在Node.js中连接到不同的数据库，你需要使用相应的库。以下是连接到MySQL, PostgreSQL, MongoDB 和 SQLite 数据库的示例代码：
- MySQL: 使用
mysql库
const mysql = require('mysql');
const connection = mysql.createConnection({
host : 'localhost',
user : 'me',
password : 'secret',
database : 'my_db'
});
connection.connect();
connection.query('SELECT 1 + 1 AS solution', (error, results, fields) => {
if (error) throw error;
console.log('The solution is: ', results[0].solution);
});
connection.end();- PostgreSQL: 使用
pg库
const { Pool } = require('pg');
const pool = new Pool({
user: 'me',
host: 'localhost',
database: 'my_db',
password: 'secret',
port: 5432,
});
pool.query('SELECT NOW()', (err, res) => {
console.log(err, res);
pool.end();
});- MongoDB: 使用
mongodb库
const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);
async function run() {
try {
await client.connect();
const database = client.db('my_database');
const collection = database.collection('my_collection');
const docs = await collection.find({}).toArray();
console.log(docs);
} finally {
await client.close();
}
}
run().catch(console.dir);- SQLite: 使用
sqlite3库
const sqlite3 = require('sqlite3').verbose();
let db = new sqlite3.Database('./database.sqlite', (err) => {
if (err) {
console.error(err.message);
} else {
console.log('Connected to the SQLite database.');
}
});
db.close((err) => {
if (err) {
console.error(err.message);
} else {
console.log('Close the database connection.');
}
});确保在使用之前安装对应的npm包，例如使用以下命令安装MySQL、PostgreSQL、MongoDB 和 SQLite 的客户端库：
npm install mysql
npm install pg
npm install mongodb
npm install sqlite3