title: How to design the schema for something like StackOverflow questions tags?
body: <p>I have 3 plans:</p>
  
  <p><strong>1, in questions table:</strong></p>
  
  <pre><code>question
  ------------------------------------
  id title   content  ...       tags
  ------------------------------------
  1  aaa     bbb      ...       tag1,tag2,tag3 (use , to split more tags)  
  </code></pre>
  
  <p><strong>2, in tags table and split:</strong></p>
  
  <pre><code>tags
  ------------------------------------
  id tag 
  ------------------------------------
  1  tag1,tag2,tag3  (use , to split more tags)
  </code></pre>
  
  <p><strong>3, in tags table:</strong></p>
  
  <pre><code>tags
  ------------------------------------
  id tag 
  ------------------------------------
  1  tag1
  2  tag2
  3  tag3 
  </code></pre>
  
  <p>I think that plan 3 is better, but what's your opinion?</p>
  
  <p>Any other good ideas for this implementation?</p>
  
  <p>Thanks for the help :)</p>