copy term reference from one to other field
You could do something like this:

$result = db_query("SELECT nid FROM {node} WHERE type = 'my_type'");
foreach($result as $row){
  $node = node_load($row-&gt;nid, NULL, TRUE); // reset cache
  // Assign one node reference field to another
  $node-&gt;field_termreference_2 = $node-&gt;field_termreference_1;
  node_save($node);
}


If you've got a lot of nodes, you may need to use the Batch API for that.

Alternatively, you may be able to copy the field tables to another field table at the database level with SQL ( backup first )

Something like:

INSERT INTO field_data_field_termreference_2 SELECT * FROM field_data_field_termreference_1;
INSERT INTO field_revision_field_termreference_2 SELECT * FROM field_revision_field_termreference_1;


and clear Drupal caches after that.