title: MySQL move data from one table to another, matching ID's
body: <p>I have (a.o.) two MySQL tables with (a.o.) the following columns:</p>
  
  <pre><code>tweets:
  -------------------------------------
  id text        from_user_id from_user
  -------------------------------------
  1  Cool tweet! 13295354     tradeny
  2  Tweeeeeeeet 43232544     bolleke
  3  Yet another 13295354     tradeny
  4  Something.. 53546443     janusz4
  
  users:
  -------------------------------------
  id from_user num_tweets from_user_id
  -------------------------------------
  1  tradeny   2235
  2  bolleke   432
  3  janusz4   5354
  </code></pre>
  
  <p>I now want to normalize the tweets table, replacing tweets.from_user with an integer that matches users.id. Secondly, I want to fill in the corresponding users.from_user_id, Finally, I want to delete tweets.from_user_id so that the end result would look like:</p>
  
  <pre><code>tweets:
  ------------------------
  id text        from_user
  ------------------------
  1  Cool tweet!     1
  2  Tweeeeeeeet     2
  3  Yet another     1
  4  Something..     3
  
  users:
  -------------------------------------
  id from_user num_tweets from_user_id
  -------------------------------------
  1  tradeny   2235       13295354
  2  bolleke   432        43232544
  3  janusz4   5354       53546443
  </code></pre>
  
  <p>My question is whether one could help me form the proper queries for this. I have only come so far:</p>
  
  <pre><code>UPDATE tweets SET from_user =
    (SELECT id FROM users WHERE from_user = tweets.from_user)
  WHERE...
  
  UPDATE users SET from_user_id =
    (SELECT from_user_id FROM tweets WHERE from_user = tweets.from_user)
  WHERE...
  
  ALTER TABLE tweets DROP from_user_id
  </code></pre>
  
  <p>Any help would be greatly appreciated :-)</p>