title: Should I drop_all() each time when I want to add a new column in sqlalchemy?
body: <p>I'm writing a simple website using Flask.
  When I added <code>time</code> field to the <code>Td</code> class I got </p>
  
  <blockquote>
    <p>sqlalchemy.exc.OperationalError</p>
    
    <p>sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) table td
    has no column named time</p>
  </blockquote>
  
  <pre><code> class Td(db.Model):
          id = db.Column(db.Integer, primary_key=True)
          text = db.Column(db.String(271), nullable=False)
          date = db.Column(db.String())
          time = db.Column(db.String())
  </code></pre>
  
  <p>I suppose that in production when you manage a big project it's not an option to <code>drop_all()</code> the whole <code>db</code> each time you add new column. 
  Is there a proper way to add a new column?</p>