pool.on('connection', function(connection) { 
    connection.query('SET SESSION auto_increment_increment=1') 
  }); 

// create 
  var poolCluster = mysql.createPoolCluster(); 
 
  poolCluster.add(config); // anonymous group 
  poolCluster.add('MASTER', masterConfig); 
  poolCluster.add('SLAVE1', slave1Config); 
  poolCluster.add('SLAVE2', slave2Config); 
 
  // Target Group : ALL(anonymous, MASTER, SLAVE1-2), Selector : round-robin(default) 
  poolCluster.getConnection(function (err, connection) {}); 
 
  // Target Group : MASTER, Selector : round-robin 
  poolCluster.getConnection('MASTER', function (err, connection) {}); 
 
  // Target Group : SLAVE1-2, Selector : order 
  // If can't connect to SLAVE1, return SLAVE2. (remove SLAVE1 in the cluster) 
  poolCluster.on('remove', function (nodeId) { 
   console.log('REMOVED NODE : ' + nodeId); // nodeId = SLAVE1  
  }); 
 
  poolCluster.getConnection('SLAVE*', 'ORDER', function (err, connection) {}); 
 
  // of namespace : of(pattern, selector) 
  poolCluster.of('*').getConnection(function (err, connection) {}); 
 
  var pool = poolCluster.of('SLAVE*', 'RANDOM'); 
  pool.getConnection(function (err, connection) {}); 
  pool.getConnection(function (err, connection) {}); 
 
  // destroy 
  poolCluster.end(); 

  connection.changeUser({user : 'john'}, function(err) { 
    if (err) throw err; 
  }); 

var db_config = { 
    host: 'localhost', 
    user: 'root', 
    password: '', 
    database: 'example' 
  }; 
 
  var connection; 
 
  function handleDisconnect() { 
   connection = mysql.createConnection(db_config); // Recreate the connection, since 
                           // the old one cannot be reused. 
 
   connection.connect(function(err) {       // The server is either down 
    if(err) {                   // or restarting (takes a while sometimes). 
     console.log('error when connecting to db:', err); 
     setTimeout(handleDisconnect, 2000); // We introduce a delay before attempting to reconnect, 
    }                   // to avoid a hot loop, and to allow our node script to 
   });                   // process asynchronous requests in the meantime. 
                       // If you're also serving http, display a 503 error. 
   connection.on('error', function(err) { 
    console.log('db error', err); 
    if(err.code === 'PROTOCOL_CONNECTION_LOST') { // Connection to the MySQL server is usually 
     handleDisconnect();             // lost due to either server restart, or a 
    } else {                   // connnection idle timeout (the wait_timeout 
     throw err;                 // server variable configures this) 
    } 
   }); 
  } 
 
  handleDisconnect(); 

var userId = 'some user provided value'; 
  var sql  = 'SELECT * FROM users WHERE id = ' + connection.escape(userId); 
  connection.query(sql, function(err, results) { 
   // ... 
  }); 
  或者使用？作为占位符 
  connection.query('SELECT * FROM users WHERE id = ?', [userId], function(err, results) { 
   // ... 
  }); 
  不同类型值的转换结果 
  Numbers 不变 
  Booleans 转换为字符串 'true' / 'false'  
  Date 对象转换为字符串 'YYYY-mm-dd HH:ii:ss' 
  Buffers 转换为是6进制字符串 
  Strings 不变 
  Arrays => ['a', 'b'] 转换为 'a', 'b' 
  嵌套数组 [['a', 'b'], ['c', 'd']] 转换为 ('a', 'b'), ('c', 'd') 
  Objects 转换为 key = 'val' pairs. 嵌套对象转换为字符串. 
  undefined / null ===> NULL 
  NaN / Infinity 不变. MySQL 不支持这些值, 除非有工具支持，否则插入这些值会引起错误. 
  转换实例： 
  var post = {id: 1, title: 'Hello MySQL'}; 
  var query = connection.query('INSERT INTO posts SET ?', post, function(err, result) { 
   // Neat! 
  }); 
  console.log(query.sql); // INSERT INTO posts SET `id` = 1, `title` = 'Hello MySQL' 

  var query = "SELECT * FROM posts WHERE title=" + mysql.escape("Hello MySQL"); 
 
  console.log(query); // SELECT * FROM posts WHERE title='Hello MySQL' 

var sorter = 'date'; 
  var query = 'SELECT * FROM posts ORDER BY ' + mysql.escapeId(sorter); 
 
  console.log(query); // SELECT * FROM posts ORDER BY `date` 
  支持转义多个 
  var sorter = 'date'; 
  var query = 'SELECT * FROM posts ORDER BY ' + mysql.escapeId('posts.' + sorter); 
 
  console.log(query); // SELECT * FROM posts ORDER BY `posts`.`date` 
  可以使用??作为标识符的占位符 
  var userId = 1; 
  var columns = ['username', 'email']; 
  var query = connection.query('SELECT ?? FROM ?? WHERE id = ?', [columns, 'users', userId], function(err, results) { 
   // ... 
  }); 
 
  console.log(query.sql); // SELECT `username`, `email` FROM `users` WHERE id = 1 

var sql = "SELECT * FROM ?? WHERE ?? = ?"; 
  var inserts = ['users', 'id', userId]; 
  sql = mysql.format(sql, inserts); 
  10、自定义格式化函数 
  connection.config.queryFormat = function (query, values) { 
   if (!values) return query; 
   return query.replace(/\:(\w+)/g, function (txt, key) { 
    if (values.hasOwnProperty(key)) { 
     return this.escape(values[key]); 
    } 
    return txt; 
   }.bind(this)); 
  }; 
 
  connection.query("UPDATE posts SET title = :title", { title: "Hello MySQL" }); 

connection.query('INSERT INTO posts SET ?', {title: 'test'}, function(err, result) { 
   if (err) throw err; 
 
   console.log(result.insertId); 
  }); 

var query = connection.query('SELECT * FROM posts'); 
  query 
   .on('error', function(err) { 
    // Handle error, an 'end' event will be emitted after this as well 
   }) 
   .on('fields', function(fields) { 
    // the field packets for the rows to follow 
   }) 
   .on('result', function(row) { 
    // Pausing the connnection is useful if your processing involves I/O 
    connection.pause(); 
 
    processRow(row, function() { 
     connection.resume(); 
    }); 
   }) 
   .on('end', function() { 
    // all rows have been received 
   }); 

connection.query('SELECT 1; SELECT 2', function(err, results) { 
   if (err) throw err; 
 
   // `results` is an array with one element for every statement in the query: 
   console.log(results[0]); // [{1: 1}] 
   console.log(results[1]); // [{2: 2}] 
  }); 

var query = connection.query('SELECT 1; SELECT 2'); 
 
  query 
   .on('fields', function(fields, index) { 
    // the fields for the result rows that follow 
   }) 
   .on('result', function(row, index) { 
    // index refers to the statement this result belongs to (starts at 0) 
   }); 

connection.beginTransaction(function(err) { 
   if (err) { throw err; } 
   connection.query('INSERT INTO posts SET title=?', title, function(err, result) { 
    if (err) {  
     connection.rollback(function() { 
      throw err; 
     }); 
    } 
 
    var log = 'Post ' + result.insertId + ' added'; 
 
    connection.query('INSERT INTO log SET data=?', log, function(err, result) { 
     if (err) {  
      connection.rollback(function() { 
       throw err; 
      }); 
     }  
     connection.commit(function(err) { 
      if (err) {  
       connection.rollback(function() { 
        throw err; 
       }); 
      } 
      console.log('success!'); 
     }); 
    }); 
   }); 
  }); 

err.code = string 
err.fatal => boolean 

function handleError (err) {
 if (err) {
  // 如果是连接断开，自动重新连接
  if (err.code === 'PROTOCOL_CONNECTION_LOST') {
   connect();
  } else {
   console.error(err.stack || err);
  }
 }
}

// 连接数据库
function connect () {
 db = mysql.createConnection(config);
 db.connect(handleError);
 db.on('error', handleError);
}

var db;
connect();

var mysql = require('mysql');
var pool = mysql.createPool(config);

pool.getConnection(function(err, connection) {
 // Use the connection
 connection.query( 'SELECT something FROM sometable', function(err, rows) {
  // And done with the connection.
  connection.end();

  // Don't use the connection here, it has been returned to the pool.
 });
});