title: How to perform a left join using OR for multiple columns
body: <p>My question is very basic as it deals with two tables: reservations and events.</p>
  
  <p>Table reservations contains 5 column which indicate the event type, this is a number. </p>
  
  <p>For example: </p>
  
  <pre><code>table reservations
  
  event_1  event_2  event_3  event_4  event_5
  181      177      485      772      474   
  </code></pre>
  
  <p>Table events contain the details about the event.</p>
  
  <p>For example:</p>
  
  <pre><code>table events
  
  id     event_key    location
  181    8888512      10
  177    2255998      88
  485    7895201      12
  772    1212855      22
  474    2125495      10
  </code></pre>
  
  <p>I would like to be able to write a query to which I will provide an event_key, and using the id from the table events, get to the reservations table. </p>
  
  <p>I have a limited knowledge of using joins, or sub-queries, I can get the idea with some explanation and help but I am unsure as to what method will get me the results I need. I hope that through this question I can get a bit of good help. </p>
  
  <p>Thank you.</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>This is the type of query I was thinking of:</p>
  
  <pre><code>SELECT 
      e.[id],
      e.[event_key],
      e.[event_location],
      e.[event_room],
      e.[event_description],
      e.[event_instructor], 
      r.[reservation_id], 
      r.[guest_first_name], 
      r.[guest_last_name], 
      r.[guest_age], 
      r.[guest_city], 
      et-cetera...
  FROM events e 
  LEFT JOIN reservations r
  ON e.id IN (r.event_1, r.event_2, r.event_3, r.event_4, r.event_5)
  WHERE e.event_key IN ('8888512', '7895201', '2125495')
  </code></pre>