title: How to use SQL CONCAT/SUBSTR?
body: <p>I am trying to create a username for each person in the marketing table.
  I want an update statement that inserts the new username into the username column.</p>
  
  <p>I want to take the first letter of the firstname, join to the first 5 letters of the surname, and save this into the username column of the marketing table. I need to put this inside a procedure somehow too.</p>
  
  <p>heres my code:</p>
  
  <pre><code>SELECT CONCAT(m.firstname, 1)||SUBSTR(m.surname, 5)
  INTO username
  FROM marketing
  WHERE marketing_id = 10001;
  </code></pre>
  
  <p>However, I am getting errors that I cannot seem to fix, like firstname and surname are invalid identifiers. Any help here is appreciated. </p>