title: sql more than one keys in one field
body: <p>I guess, the name of the question is strange, but I don't know how to state it correctly, so I'll try to describe the problem. Say, we have two tables:</p>
  
  <p>1)</p>
  
  <pre><code>id | unit_name | strength | health
  1  | private   | 10       | 10
  2  | general   | 5        | 5
  n  | someone   | 123      | 321
  </code></pre>
  
  <p>2)</p>
  
  <pre><code>id | rules | who_has_this_rule
  1  | rule1 | 1
  2  | rule2 | 2
  3  | rule3 | 1
  4  | rule4 | 1
  </code></pre>
  
  <p>The field "who_has_this_rule" correspondes with id of the first table.
  But I can't figure out what to do if a unit should have more than one rule in his profile. For example, private should have rule1 and rule4. How to do this?</p>