title: mysql - join where right hand table has ALL required
body: <p>I have t1:</p>
  
  <pre><code>vid  vs
  1     1
  1     2
  1     3
  2     2
  2     3
  3     1
  3     3
  </code></pre>
  
  <p>and t2</p>
  
  <pre><code>pid  ps
  1     2
  1     3
  2     1
  2     3
  </code></pre>
  
  <p>I need ONLY t2.pid, t1.vid where all required t1.vs are in t2.ps for the respective t2.pid:</p>
  
  <pre><code>pid  vid
    1    1
    1    2
    2    1
    2    3
  </code></pre>
  
  <p>So, vid 3 is not selected for pid 1 as ps 2 is not in vs...</p>
  
  <p>I'm getting tangled up in joins here... Help?</p>