l>
<li>implicit <code>not null</code> for each primary key column</li>
</ul></li>
<li>We can use a column constraint if the primary key has only 1 column
<ul>
<li><code>sid integer primary key</code></li>
</ul></li>
<li>If the primary key has more than 1 column, we must use a table constraint
<ul>
<li>specified after all columns in the <code>create table</code> statement</li>
<li><code>primary key(eid, sid)</code></li>
</ul></li>
</ul>
<h3 id="unique-constraints">Unique Constraints</h3>
<ul>
<li>Like primar