title: Flink table left outer join showing an error
body: <p>I am doing a <strong>left outer join</strong> on two tables in flink, and the code is given below, showing an exception, <strong>inner join</strong> with the same two tables worked fine and was able to convert to Datastream</p>
  <pre><code>Table table = customerTable.leftOuterJoin(contactTable,$(&quot;cust_custcode&quot;)
  .isEqual($(&quot;contact_custcode&quot;)))
  .select($(&quot;customermessage&quot;), $(&quot;contactmessage&quot;));
  </code></pre>
  <p>The exception is : org.apache.flink.table.api.TableException: Table sink '<em>anonymous_datastream_sink$3</em>' doesn't support consuming update and delete changes which is produced by node Join(joinType=[LeftOuterJoin], where=[(f0 = f00)], select=[f0, f1, f00, f10], leftInputSpec=[NoUniqueKey], rightInputSpec=[NoUniqueKey])</p>