title: Error when perform query select left join select where
body: <p>I have 2 tables:</p>
  
  <pre><code>CREATE TABLE Student_registration (
      id INT AUTO_INCREMENT PRIMARY KEY,
      Name VARCHAR(255) NOT NULL,
      Contact VARCHAR(255) NOT NULL,
      regdatetime TIMESTAMP DEFAULT CURRENT_TIMESTAMP
  );
  
  CREATE TABLE timestamp_table (
      id INT AUTO_INCREMENT PRIMARY KEY,
      timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP
  );
  </code></pre>
  
  <p>When I perform this query:   </p>
  
  <pre><code>select *
     from Student_registration
     LEFT JOIN (select count(*)
              from Student_registration)
      where RegDateTime &gt; (select timestamp
                              from timestamp_table
                              where id= 1);
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>ERROR 1248 (42000): Every derived table must have its own alias
  </code></pre>
  
  <p>How do I fix this?</p>