title: Pentaho Data Integration Multiway Merge Join
body: <p>I want to use the Multiway Merge Join step in Pentaho?  The documentation is woefully lacking, and it's not doing what I intuitively thought it would do.</p>
  
  <p>I have the following tables defined in Oracle:</p>
  
  <pre><code>JOE1:
  A   B   C
  1   NY  3
  2   NJ  1
  3   NJ  3
  4   CT  7
  
  JOE2:
  B   D
  CT  Connecticut
  NJ  New Jersey
  NY  New York
  
  JOE3:
  C   E
  1   one
  3   three
  7   seven
  </code></pre>
  
  <p>Here's the metadata from my Multiway Merge Join step in my .ktr:</p>
  
  <pre><code>Step name:  Multiway Merge Join
  
  Input Table1:  JOE1    Join Keys: B,C
  Input Table2:  JOE2    Join Keys: B
  Input Table3:  JOE3    Join Keys: C
  Join Type:  INNER
  </code></pre>
  
  <p>I would've expected my .ktr to produce something like this:</p>
  
  <pre><code>A   B   C   B_1 D           C_1 E
  1   NY  3   NY  New York    3   three
  2   NJ  1   NJ  New Jersey  1   one
  3   NJ  3   NJ  New Jersey  3   three
  4   CT  7   CT  Connecticut 7   seven
  </code></pre>
  
  <p>But, instead, I get the following error:</p>
  
  <pre><code>**2018/10/12 14:44:25 - Multiway Merge Join.0 - Unexpected conversion error while converting value [B String(2)] to an Integer
  2018/10/12 14:44:25 - Multiway Merge Join.0 - 
  2018/10/12 14:44:25 - Multiway Merge Join.0 - B String(2) : couldn't convert String to Integer
  2018/10/12 14:44:25 - Multiway Merge Join.0 - 
  2018/10/12 14:44:25 - Multiway Merge Join.0 - B String(2) : couldn't convert String to number : non-numeric character found at position 1 for value [CT]**
  </code></pre>
  
  <p>This is an indication that it's not joining on the field I defined to join on in the .ktr.</p>
  
  <p>Unfortunately, my company's firewall prevents me from sending a link to any files or images.  I'm hoping I've provided enough information for someone to advise me if I've done something wrong or even if my behavioral expectations are accurate.</p>