Can a table have a surrogate key without a (natural) alternate key?
<p>I think it doesn't make sense for a table to have a surrogate key without also having a (natural) alternate key (keep in mind that one of the properties for a surrogate key is that it has no meaning outside the database environment).</p>

<p>For example say I have the following table:</p>

<p><a href="https://i.stack.imgur.com/RI68r.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RI68r.png" alt="enter image description here"></a></p>

<p>Say that <code>employee_id</code> is the surrogate primary key, and there is no (natural) alternate key in the table.</p>

<p>Now let's say that some employee wants to change his phone number, how can we identify the record for this employee in the table? we can't identify it using the surrogate key, because the surrogate key is not known in the real world (i.e. we don't know the <code>employee_id</code> for each employee).</p>

<p>So there must be a (natural) alternate key in the table to identify each employee in the real world (for example: <code>SSN</code>).</p>

<p>Am I correct, or am I missing something?</p>