title: Replacing any NULL fields with a string
body: <p>I'm new to SQL and this problem has stumped me. I am supposed to write an SQL statement that lists all the data in a table, but if a column might contain NULL values (in this case only one field is NULL), the phrase "-NONE-" must print in that column for that row. The lab hints that I must use one or more single-row functions to accomplish this. </p>
  
  <p>We are using Oracle SQL Developer to test scripts. I am trying to use the REPLACE function but I keep getting errors. I've tried using NVAL, REPLACE, and other similar functions but I am clearly getting the syntax wrong. For example:</p>
  
  <pre><code>SELECT *, REPLACE(manager_id, NULL, '-NONE-')
  FROM departments;
  </code></pre>
  
  <p>^Always returns an error: missing FROM statement where expected</p>