var Joi = require('joi');

var schema = Joi.object().keys({
    username: Joi.string().alphanum().min(3).max(30).required(),
    password: Joi.string().regex(/^[a-zA-Z0-9]{3,30}$/),
    access_token: [Joi.string(), Joi.number()],
    birthyear: Joi.number().integer().min(1900).max(2013),
    email: Joi.string().email()
}).with('username', 'birthyear').without('password', 'access_token');

Joi.validate({ username: 'abc', birthyear: 1994 }, schema, function (err, value) {
    if(err){
        // HANDLE VALIDATION ERROR
    }
    else {
        // DO DATABASE OPERATIONS HERE
    }
 });