title: Merge two columns and find corresponding name to another filed
body: <p>I have a table names "staff". This table has 10 columns: staffno, fname, lname, position, sex, dob, salary, branchno and manager. The column "manager" is the staffno of the persons manager if he/she has one, and NULL otherwise. </p>
  
  <p>I want to find the name of each staff member and their manager too if they have one and merge the first name and last name in one column.</p>
  
  <p>My code is as below:</p>
  
  <pre><code>SELECT CONCAT(staff.fname, ' ', staff.lname) AS StaffName ,
  CONCAT(staff.fname, ' ', staff.lname) AS ManagerName
  FROM staff WHERE staff.manager IS NOT NULL AND staff.staffno = staff.manager;
  </code></pre>
  
  <p>Is this code correct?</p>