ints">
<h1>Constraints<a class="headerlink" href="#constraints" title="Permalink to this headline">¶</a></h1>
<p>Constraints are defined per field and control its content. Currently, two
types of constraints are supported:</p>
<ul class="simple">
<li>Whether a field is mandatory/required and the user needs to fill it</li>
<li>Whether a field should have unique content and no two rows can exist in the
database with the same value of this field</li>
</ul>
<p>In our library/book example, we define a name of t