title: "is not null" vs boolean MySQL - Performance
body: <p>I have a column that is a datetime, <code>converted_at</code>.</p>
  
  <p>I plan on making calls that check <code>WHERE converted_at is not null</code> very often. As such, I'm considering having a boolean field <code>converted</code>. Is their a significant performance difference between checking if a field is <code>not null</code> vs if it is <code>false</code>?</p>
  
  <p>Thanks.</p>