SQL Query

<?php
/**
 * Created by PhpStorm.
 * User: sr
 * Date: 17/04/17
 * Time: 16:01
 */
/*
 Given the two tables below, write a SQL query that uses a join statement to list all users from the user table, their average correct answers, as well as the time of their most recently taken test. All user entries should appear, even if they have not taken a test.

 */

$sql = "

  SELECT user.user_id, CONCAT(user.first_name, ' ', user.last_name) as full_name, test_result.test_id, AVG(test_result.correct) as avg_correct, MAX(test_result.time_taken) as recent_time

  FROM user

  LEFT JOIN test_result ON test_result.user_id = user.user_id

  GROUP BY user.user_id

  ORDER BY recent_time DESC;
  -- ORDER BY `avg_correct` DESC, recent_time DESC;
";