title: mysql query within a query with privacy condition check
body: <p>I have 3 tables.</p>
  
  <pre><code>myMembers
  ------------------------------------
  id | username | privacy
  ------------------------------------
  1  | userA    | 0
  2  | userB    | 1
  3  | userC    | 0
  4  | userD    | 1
  
  following
  --------------------------------
  id  | user_id  | follower_id
  --------------------------------
  1   | 2        | 1
  
  posts
  -------------------------------------
  id  |  userID | username   | statusMsg
  --------------------------------------
  1   |  4      | userD    | Issac Newton is genius
  2   |  2      | userB    | Newton Saw apple
  3   |  3      | userC    | Newtonian Physics
  4   |  1      | userA    | Calculus came from Sir Newton
  </code></pre>
  
  <p>There is a search field. When a logged in user searches for 'keyword' in table 'posts', I want to omit results from those users who has set his privacy to '1'  and WHERE searcher is not following user B.</p>
  
  <p>The query should logically do this.</p>
  
  <pre><code>SELECT * from posts WHERE (match the keyword) 
              AND ( 
                  if (poster's privacy (which is set in myMembers)==1){
                      if (seacher is following poster){
                          select this post
                      }
                  }
                     else { select this post
                  }
               )
                     LIMIT results to 5 rows
  </code></pre>
  
  <p>So for a keyword "Newton",
  if userA is searching, rows 2,3,4 from 'posts' should be returned.
  if userD is searching, only rows 1, 3 and 4 from 'posts' should be returned, </p>
  
  <p>based on privacy and following
  Edit: Tagging for future searches: IF condition within WHERE Clause in mySql</p>