MySQL LEFT JOIN with NULL : <p>I have the following querie:</p>

<pre><code>SELECT *
FROM work
LEFT JOIN users ON work.user_id = users.user_id
LEFT JOIN customer ON work.customer_id = customer.customer_id
WHERE customer.visible = 0 
</code></pre>

<p>the problem is about the "LEFT JOIN customer ON..." and the WHERE condition "customer.visible = 0 ".
I have entries in my table "work" where "customer_id = NULL" and they get removed from the select because there obviously is no customer with ID "NULL" in the customer table.</p>

<p>I would like to keep all entries where "customer_id = NULL" in my work table.</p>
