title: Set value to NULL in MySQL
body: <p>I want a value to be set to <code>NULL</code> if nothing is put into the text box in the form I'm submitting. How can I make this happen?
  I've tried inserting <code>'NULL'</code> but this just adds the word <code>NULL</code> into the field.</p>
  
  <p>I'm not sure what code I should provide for this, I'm just writing an UPDATE query.</p>