nodejs之express 创建数据库连接

//server/db.js
// 创建数据库连接
const mysql = require("mysql")
const connection = mysql.createConnection({
    host: "ip地址",
    port: 3306,
    user: "用户名",
    password: "密码",
    database: "数据库名"
})
connection.connect((err) => {
    if (err) { console.log("连接失败") }
    else { console.log("连接成功") }
})
 
let query=(sql, callback)=>{
    connection.query(sql, function (err, rows) {
        callback(err, rows);
    });
    // connection.end();//end()的话好像就只能连接一次的样子
}

//routes/user.js
var express = require('express');
var router = express.Router();
var db = require("../server/db");

router.get('/', function(req, res, next) {
  let sql="select * from 表名"
  db.query(sql,(err,rows)=>{
    if(err){
      res.json({err:"sql语句错误"})
    }
    else{
      res.json({
        code: 200,
        message: "成功",
        data: {
          list: rows
        }
      })
    }
  })
})

module.exports = router;