title: How do I get rows with value1 in column1 and value2 in column2 but value2 in column1 does not have value1 in column2?
body: <p>I have a table called <code>contacts</code>:</p>
  
  <pre><code>user_id     contact_id
  10294       10295
  10294       10293
  10293       10294
  10295       10296
  10296       10294
  10297       10296
  10298       10295
  10295       10294
  10293       10297
  </code></pre>
  
  <p>How can I select the rows from this table where <code>user_id</code> has a <code>contact_id</code> but the feeling is not reciprocated - I mean that <code>contact_id</code> does not have <code>user_id</code> as a <code>contact_id</code>?</p>
  
  <p>For example in the above case <code>$user_id</code> is <code>10295</code>. The row I want is</p>
  
  <pre><code>   10295       10296
  </code></pre>
  
  <p>I can select all rows with <code>user_id</code> as <code>10295</code> with:</p>
  
  <pre><code>        $sql = "SELECT * FROM contacts 
          WHERE user_id = ?";  
  
          $stmt2 = $con-&gt;prepare($sql) or die(mysqli_error($con));
          $stmt2-&gt;bind_param('i', $user_id) or die ("MySQLi-stmt binding failed ".$stmt2-&gt;error);
          $stmt2-&gt;execute() or die ("MySQLi-stmt execute failed ".$stmt2-&gt;error);
  
          $privateReviews = $stmt2-&gt;get_result(); 
  </code></pre>
  
  <p>It would give me:</p>
  
  <pre><code>10295       10296
  10295       10294
  </code></pre>
  
  <p>But I am looking for just: <code>10295       10296</code>.</p>
  
  <p>How can I do this?</p>