How to connect nodejs to MySQL database

This article mainly introduces the function of connecting to the MySQL database implemented by nodejs. It analyzes the related operation steps and implementation skills of nodejs connection and querying mysql data in the form of examples. Friends in need can refer to it. I hope it can help everyone.

1. Run npm install mysql in the project directory to install the mysql module for nodejs;

2. Create db.js for the module To connect to mysql, define query query method at the same time;

var mysql = require('mysql');
// 创建一个数据库连接池
var pool = mysql.createPool({
 connectionLimit: 50,
 host: 'localhost',
 user: 'admin',
 password: '123456',
 database: 'rp-test'
});
// SELECT * FROM users
// 让我们的方法支持两种模式
// 一种是只传入SQL语句和回调函数
// 一种是传入SQL语句、参数数据、回调函数
exports.query = function (sql, P, C) {
 var params = [];
 var callback;
 // 如果用户传入了两个参数，就是SQL和callback
 if (arguments.length == 2 && typeof arguments[1] == 'function') {
  callback = P;
 } else if (arguments.length == 3 && Array.isArray(arguments[1]) && typeof arguments[2] == 'function') {
  params = P;
  callback = C;
 } else {
  throw new Error('对不起，参数个数不匹配或者参数类型错误');
 }
 // 如果用户传入了三个参数，那么就是SQL和参数数组、回调函数
 // 从池子里面拿一个可以使用的连接
 pool.getConnection(function (err, connection) {
  // Use the connection
  connection.query(sql, params, function () {
   // 使用完毕之后，将该连接释放回连接池
   connection.release();
   callback.apply(null, arguments);
  });
 });
};

3. Query example

var express = require('express');
var db = require('./db');
var router = express.Router();
router.get('/',function(req, res, next){
  db.query("select * from app",function(err,result){
     //console.log(result);
    res.send(JSON.stringify (result));
  });
});
module.exports=router;

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