db mysql pool in nodejs

gistfile1.txt

"use strict";
var mysqlClient = require('mysql')
  , dbPool = mysqlClient.createPool(require('../config/database'))
  , commonHelper = require('../library/commonHelper');

function MyModel(params) {
  this.tbl = params.tbl;
  this.primary_key = params.primary_key;
  this.primary_name = params.primary_name;
  this.dbPool = dbPool;
}

module.exports = MyModel;

//primary key
MyModel.prototype.fromPK = function fromPK(pk, callback) {
  //I think i can define var t = this here and access it in below function. but will i need to do this for every other functions i define?
  this.dbPool.getConnection(function (err, connection) {
    //I cannot access this here from main class. 
    var query = "SELECT * FROM " + this.tbl + " WHERE " + this.primary_key + " = " + connection.escape(pk);
    connection.query(query, callback);
  });
};
//primary name
MyModel.prototype.fromPN = function fromPN(pn, callback) {
  this.dbPool.getConnection(function (err, connection) {
    var query = "SELECT * FROM " + this.tbl + " WHERE " + this.primary_name + " = " + connection.escape(pn);
    connection.query(query, callback);
  });
};