title: Hive: Left outer join with rlike condition
body: <p>As we know theta joins (non equality joins) are not supported by hive. </p>
  
  <p>In a normal join I would have handled it something like:</p>
  
  <pre><code>Select t.A, t.B, u.D
  from table t
  join uTable u
  where t.C rlike u.C
  </code></pre>
  
  <p>Now, I want to do a left join. Putting rlike in where condition will filter out non matches and result wont have null values keys.
  How to handle this scenario in hive?</p>
  
  <p>During playing around I found this approach. Is this a right start?</p>
  
  <pre><code>Select t.A, t.B, u.D
  from table t
  left outer join uTable u
  where ( t.C rlike u.C
  or t.C rlike '' )
  </code></pre>