title: How to use left join after where clause
body: <p>I have two table:</p>
  
  <pre><code>// comment 
  +----+---------+---------+----------------------+
  | id | id_post | user_id |       content        |
  +----+---------+---------+----------------------+
  | 1  |  1111   |  2222   |   this is content1   |
  | 2  |  3333   |  2222   |   this is content2   |
  | 3  |  3333   |  4444   |   this is content3   |
  +----+---------+---------+----------------------+
  
  // user
  +------+-----------+
  |  id  |   name    |
  +------+-----------+
  | 2222 |   jack    |
  | 4444 |   peter   |
  +------+-----------+
  </code></pre>
  
  <p>And here is my query:</p>
  
  <pre><code>select c.content, u.name
    from comment c inner join user u on c.id_user = u.id
    where c.id_post = 3333;
  </code></pre>
  
  <p>And here is my result:</p>
  
  <pre><code>+----------------------+-----------+
  |        content       |   name    |
  +----------------------+-----------+
  |   this is content2   |   jack    |
  |   this is content3   |   peter   |
  +----------------------+-----------+
  </code></pre>
  
  <hr>
  
  <p>So, <strong>My question</strong>: I need to add one more column contained <code>1</code> number <em>but just for specific user</em>. In other word <strong>I want this output</strong>:</p>
  
  <pre><code>// for this user: 2222 (or jack)
  +----------------------+-----------+----------+
  |        content       |   name    | user_id  |
  +----------------------+-----------+----------|
  |   this is content2   |   jack    |    1     |
  |   this is content3   |   peter   |          |
  +----------------------+-----------+----------+
  
  // for this user: 444  (or peter)
  +----------------------+-----------+----------+
  |        content       |   name    | user_id  |
  +----------------------+-----------+----------|
  |   this is content2   |   jack    |          |
  |   this is content3   |   peter   |     1    |
  +----------------------+-----------+----------+
  </code></pre>
  
  <p>I think I should use one more <code>left join</code>, but I don't know how should I add one <code>left join</code> to my query. there is any suggestion ?</p>