Insert/Update in JDBC stage

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There is actually a workaround for this, using the JDBC Query Executor. You can specify the 'query' to be anything. For example, I'm using a JDBC Query Executor with MySQL and a query of the form:

INSERT INTO mytable (column_pk, column_a, column_b) 
VALUES('${record:value('/pk')}',
       '${record:value('/a')}',
       '${record:value('/b')}')
  ON DUPLICATE KEY UPDATE 
    b=VALUES(b),
    c=VALUES(c)

You'll need to change the SQL according to the database that you're working with.