npm install --save mysql

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

connect.end(function(err){
  console.log('End a connection');
});

var mysql = require('mysql');
var option = require('./connect.js').option;
var conn = mysql.createConnection(option);
conn.query('select * from message',function(err,rows,fields){
 if(!err){
  console.log(rows);
 }
});
conn.end(function(err){
 console.log('end a connection');
});

var mysql = require('mysql');
var pool = mysql.createPool({
 connectionLimit : 10,
 host      : 'example.org',
 user      : 'bob',
 password    : 'secret',
 database    : 'my_db'
});
pool.query('SELECT 1 + 1 AS solution', function(err, rows, fields) {
 if (err) throw err;
 console.log('The solution is: ', rows[0].solution);
});

var mysql = require('mysql');
var pool = mysql.createPool({
 host   : 'example.org',
 user   : 'bob',
 password : 'secret',
 database : 'my_db'
});
pool.getConnection(function(err, connection) {
 // Use the connection
 connection.query( 'SELECT something FROM sometable', function(err, rows) {
  // And done with the connection.
  connection.release();
  // Don't use the connection here, it has been returned to the pool.
 });

// Use the connection
 connection.query( 'SELECT something2 FROM sometable2', function(err, rows) {
  // And done with the connection.
  connection.release();
  // Don't use the connection here, it has been returned to the pool.
 });
});

// connect.js 数据库连接与关闭
var mysql = require('mysql');
var config = require('./config.json'); // 将数据库连接参数写入mysql对象，即config.mysql
var connCount = 0; // 统计目前未关闭的连接
exports.getConn = function(){
 connCount ++;
 console.log('............................OPEN a connection, has '+ connCount + ' connection.');
 return mysql.createConnection(config.mysql);
};
exports.endConn = function(conn){
 conn.end(function(err){
  if(!err){
   connCount --;
   console.log('.........................CLOSE a connection, has '+ connCount + ' connection.');
  }
 });
};

// db.js 查询用户信息
var connect = require('./connect.js'); // 引入数据连接方法
exports.getUser = function(username, callback){
  var connection = connect.getConn();
  var sql = 'select * from user where username = "' + username + '"';
  connection.query(sql,function(err,rows,fields){
    callback(err,rows,fields);  
  });
  connect.endConn(connection);
}

// connect.js 直接使用
var mysql = require('mysql');
var config = require('./config.json');
var pool = mysql.createPool(config.mysql);

exports.querySQL = function(sql,callback){
  pool.query(sql, function(err,rows,fields){
    callback(err,rows,fields);
  });
}

// connect.js 使用getConnection方法
var mysql = require('mysql');
var config = require('./config.json');
var pool = mysql.createPool(config.mysql);

exports.querySQL = function(sql, callback){
  pool.getConnection(function(err,conn){
    conn.query(sql,function(err,rows,fields){
      callback(err,rows,fields); 
      conn.release();  // 不要忘了释放
    });    
  });
}

// db.js 查询用户信息
var connect = require('./connect.js');
exports.getUser = function(username,callback){
  var sql = 'select * from user where username = "' + username + '"';
  connect.querySQL(sql,function(err,rows,fields){
    callback(err,rows,fields);    
  });
};