npm install mysql

var mysql   = require('mysql'); 
var connection = mysql.createConnection({ 
 host   : 'localhost', 
 user   : 'root', 
 password : '123456', 
 database : 'nodejs' 
}); 
 
connection.connect(); 
 
connection.query('SELECT 1 + 1 AS solution', function(err, rows, fields) { 
 if (err) { 
  console.log(err); 
  return; 
 }; 
 
 console.log('The solution is: ', rows[0].solution); 
}); 
 
connection.end(); 

var db  = {}; 
var mysql = require('mysql'); 
var pool = mysql.createPool({ 
 connectionLimit : 10, 
 host      : 'localhost', 
 user      : 'root', 
 password    : '123456', 
 database    : 'nodejs' 
}); 
 
db.query = function(sql, callback){ 
 
  if (!sql) { 
    callback(); 
    return; 
  } 
  pool.query(sql, function(err, rows, fields) { 
   if (err) { 
    console.log(err); 
    callback(err, null); 
    return; 
   }; 
 
   callback(null, rows, fields); 
  }); 
} 
module.exports = db; 

var db = require('./mysql.js'); 
var sql = 'SELECT count(*) as count from user'; 
db.query(sql, function(err, rows, fields){ 
  if (err) { 
    console.log(err); 
    return; 
  } 
  console.log('用户数量 : ', rows[0].count); 
});