Data Mapper, Repository and Unit of Work patterns
<p>I'm learning about the following patterns</p>

<ul>
<li>Data Mapper</li>
<li>Repository</li>
<li>Unit of Work</li>
</ul>

<p>I think I understand each of them but I can't answer these questions</p>

<ul>
<li>are they always used to together?</li>
<li>which pattern uses the others?</li>
<li>which pattern is known by the Domain Model?</li>
<li>what CRUD operations are handled by each of them?</li>
<li>who owns the database code (i.e. SQL)?</li>
</ul>

<p>Thanks.</p>